CALIFORNIA MILITARY DEPARTMENT HISTORY PROGRAM 2814 B Street

Sacramento, CA 95816

Harbor Defenses of San Francisco

Government Leased Military Reservation, Lands End

By Matthew W. Kent

Digitized 7 September 2018

Summer 2018 1he Coast D efense j ournal

Government Leased Military Reservation Lands End, Harbor Defenses of San Francisco

Matthew W Kent

Reservation Established

Page SJ

With little existing anti-motor torpedo boat (AMTB) armament at the Golden Gate and the entrance to San Francisco Bay at the beginning of World War II in 1941, new AMTB 90 mm bat­teries needed to be constructed within the Harbor Defenses of San Francisco (HDSF). To strengthen the AMTB defenses along the Golden Gate Straights, new land was acquired at Lands End, north of Fort Miley. On September 15, 1942, the War Department leased 55.35 acres at Lands End from. the City and County of San Francisco for the construction of gun and seacoast searchlight positions. The acquisition was approved under the general directive, Hq. Northern California Sector, file 601.53, to the Commanding Officer, Harbor Defenses of San Francisco, dated 17 August 1942, Subject: "Leases -Harbor Defenses of San Francisco," and by letter, Office of the Chief of Engineers, file 601.53 (Harbor Defenses, San Francisco) SPELS, to the Division Engineer, South Pacific Division, dated 31 July 1942, Subject: ''Acquisition of Land for Harbor Defenses of San Francisco."(!)

Three 90 mm batteries, each consisting of two M 1 90 mm guns on fixed M3 carriages and two 90 mm guns on M lAl mobile carriages, were allotted to the HDSF for siting at Gravelly Beach, Baker Beach, and Lands End by the 3rd Indorsement, The Adjutant General's Office, file AG 660.2 (5-8-43) OB-S-E, 1 June 1943, to secret letter, Hq. Harbor Defenses of San Francisco, file 660.2, to the Com­manding General, Western Defense Command, dated 8 May 1943, subject: "90 mm Ami-Motor Torpedo Boat Batteries."(2)

90mmAAGun

In 1938, the U.S. Army issued requirements for the development of antiaircraft guns to counter continued increases in aircraft size, speed, and altitude. The 90 mm Tl model was tested that same year, and modifications and improvements suggested by the testing produced the T2, which was ad­opted and put into production as the Ml in 1940. By the time the United States entered the war in December 1941 , the army had 171 Ml 90 mm guns, and the very high-priority production of Ml guns continued into 1942. The M 1 gun was a powerful weapon, with a 50-caliber barrel and a verti­cal sliding wedge breech mechanism, using an inertia-type firing mechanism, a modification of the continuous pull type. The 90 mm guns fired 73 lb. HE shells at 2,700 fps, to a range of 19,000 yds., limited by the proximity fuze (1944) , or 11 ,273 yds ., limited by the 30-sec. time fuze (1944). Manual loading was standard for the M 1 gun in the antiaircraft role, but a rammer was designed for it. The rammer worked on the basis of recoil, so one round had to be loaded and fired in the normal manner before the rammer was operational . On the M 1 mount, the gun had a rate of fire of 22 rpm.

Recoil was controlled by a hydro-pneumatic system, which used a recoil cylinder, a gas cylinder, and a floating piston cylinder, all placed under the barrel. The recoil was variable, ranging from 40-44 inches at 0° elevation to 24½-26 inches at 80°. A single equilibrator balanced the weight of the barrel, allowing the gun to be trunnioned near the breech.The Ml mount operated manually only, while the MlAl mount was designed to work with the M2 remote control system. The gun sat on a single-axle trailer mount, with a trail and three outriggers for stability.

Volume 32, Issue 3 The Coast D efense journal Page 54

SffiER, FUZE, M13

TRAIL FIRING PLATFORM

BOGIE

Fig. 1. Ml 90 mm gun. TM 9-370 (GPO, 1947)

Ml 90 mm Gun on M3 Fixed Mount

The M l gun was also mounted on the M3 (originally the T3) mount. This fixed mount was in­stalled on a concrete emplacement, with a shield to protect the gun and crew. This manually-loaded mount was used in the seacoast role, but could be used against aircraft. Like the M lAl mount, it used a remote control system, in this case the Ml 3. The 90 mm gun on the M 3 mount had a maximum rate of fire of 30 rpm, and a normal rate of 25 rpm.(3) (Fig. 1)

The fixed gun consisted of the 90 mm gun Ml and top carriage MlAl on the 90 mm gun mount M3. The mount M3 had shielding of boiler plates, providing fragmentation protection only. No shielding was provided at the rear due to the requirements for service of the piece. A sighting port in the shield in front permitted the gun pointer sighting in azimuth. The upper part of the opening was provided for the movement of the gun in elevation, and depression was protected with a sliding shield attached to the cradle. The shield allowed 360° traverse and was capable of elevating from -8° to +80°. The maximum effective range of the gun was approximately 10,000 yards. The gun data com­puter, which was eventually to be supplied as part of the standard fire control equipment for this gun, provides for operation up to 19,5 00 yards. This permitted tracking considerably in advance of the time when fire could be brought to bear on the target. The sighting equipment for case II pointing included an M6 8-power elbow telescope with a field of view of 8°45' . The telescope mount afforded deflection settings of plus or minus 7° with 10 as the normal reading. The M 13 remote control system was used, giving an expected rate of fire of 25 round per minute.

Ammunition provided was the ~1- high-explosive shell with an M48 point-detonating fuze and M20 booster. The ammunition came sealed in a fiber container, complete with booster and fuze. The fuze could be set for superquick or .05-second delay, with both actions initiated on impact. Normally the bulk of the ammunition \\·as m be srored in the battery emplacement, with alert ammunition stored at each gun emplacement i,1 a COilcrece boxlike shelter called an ammunition pit. The ammuni­tion in this pit was ro be kep;: .eacy fo , i.._-n~ediate use with the fuzes set for delay action.

Summer 2018 The Coast D efense j ournal Page 55

The gun section of the fixed 90 mm gun was composed of nine men in the gun squad and six men in the ammunition squad. One artillery mechanic was assigned to the battery as part of the machine gun and executive officer's detail. The gun squad consisted of a gun commander, chief of breech, No. 1 (elevation setter), No. 2 (gun pointer), No. 3 (loader), Nos. 4, 5, 6 (ammunition relayers); and No. 7 (empty cartridge handler), while the ammunition squad consisted of a chief of ammunition, Nos. 8, 9, 10, 11, (ammunition handlers), and one basic private, who worked with the squad when not needed elsewhere.(4) (Figs. 2 & 3)

90 mm Gun Ml and Gun Mount T3

Gun Tube: Caliber Length of bore Length of gun cube Weight Projectile travel in barrel Length of rifling Number of grooves

Ammunition: Weight of round (H.E., M 7 1) Weight of projectile (H.E., M71) Weight of powder charge (H.E., M71)

Chamber capacity (cartridge case) Maximum powder pressure Muzzle energy Muzzle velocity

90mm 50 calibers 186.15 in. 1,465 lb. 156.4 in. 152.4 in. 32

41.9316. 23 .2916. 7.3116.

300 cu in. 38,000 lb. per sq. in. 1,324.4 ft. -ton 2,700 ft. per sec.(5)

Battery Land

A 90 mm AMTB battery to be constructed at the Lands End Government Leased Reservation located at the northernmost tip of Lands End would provide a field of fire of the entire Golden Gate Sciaic. Work commenced on June 29, 1943, on a battery of two 90 mm Ml guns on M3 fixed carriag­es, mounted on reinforced concrete gun plugs 120 feet apart, at an elevation of 84.59 feet M.L.L.W, separated by the rocky spine of Lands End proper. The concrete gun plugs were 14 feet in diameter and approximately 5 feet chick, with a rectangular conduit hatch adjacent to the bole circle providing access to electrical and communication cabling and equipment. (Fig. 4) The bole circle diameter was 3' 1 O", with 16 spaced boles for mounting the gun. Each concrete gun plug was surrounded by a 6-foot-wide crushed rock "working circle" of compacted gravel chat gave the gun crews additional maneuvering room to man the guns.(Fig. 5) Work on the battery was completed on September 6, 1943, at a cost of $13,049.78. For reasons unclear, the new 90 mm AMTB battery, Battery Land, was not officiall transferred to the coast artillery until January 18, 1944.(6) It is more than likely that the guns were in service the entire time with the January 1944 dace merely a record-keeping convenience.

Volume 32, Issue 3 7he Coast D efense j ournal Page 56

Fig. 2. Figure 2. 90 mm gun Ml and 90 mm gun mount T3. TM 9-373, (GPO, 1943)

SLIDING SHIELD------ ---- --~

CLEARANCE FOR TELESCOPE------

'V ~ TRAVERSING SIGHTING HOLE

~ ------LEFT SHIELD

I ""'"'"G sG,nNG "°"~

•G"' '"'"" I . ' ~~4; lfZ.:4 1--------------- RECOIL MECHANISM

I CRADLE

ELEVATING RACK ----~•-----------a " A" END SHIELD •- p, REMOTE CONTROL CONDUITS

~ G ., .. ...

I EQUILIBRATOR

BASE RING · ~ ... ,,,,..- PEDESTAL

RA PD 61978

Fig. 3. 90 mm gun l\fl and T3 gun mount . TM 9-373, (GPO, 1943)

Summer 201 8 ~e Coast D efense journal Page 57

MANHOLE ]

. -.,

. mm ·:- , .- ·, . - , · ... . ft .. ~

RA PD 6201 7

Fig. 4. 90 mm gun - Typical concrete base. TM 9-373, ( GPO, 1943)

Gun No. 1 was an Ml 90 mm gun, serial No. 15522, mounted on an M3 fixed mount, serial No. 228. Gun No. 2 was an Ml 90 mm gun, serial No. 15676, mounted on an M3 fixed mount, serial No. 239. Both guns were manufactured by Watervliet Arsenal, and both mounts were by Fisher Body Works.(7) Of note, no ammunition was fired from July 1, 1945, through December 31, 1945. A total of 344 rounds of ammunition were fired from the installation of the armament at the battery until December 31, 1945; 179 rounds for Gun No. 1 and 165 rounds for Gun No. 2.(8) In addition to the two 90 mm Ml guns on M3 (fixed) mounts, two 90 mm Ml guns mounted on MlAl antiaircraft carriages were allotted under the War Department authorization, but it is unknown if the battery ever received its two mm MlAl guns. (9)

Battery Land was to be provided with improvised dug-in rype magazines at each gun position during wartime for local ammunition storage. During peace, the ammunition for all AMTB barteries south of the Golden Gate was to be stored at the central reserve magazine, located at Fort Winfield Scott.(10) It is unknown if the magazines or any other temporary support structures were constructed at the battery, since no structures are listed on the 1944 Historical Record of Engineer Property Re­port. Standby electric power was provided to the battery by an M7 portable generating unit with an output of 37.5 kVA, 3 phase, 110 volt. Data transmission was accomplished with remote control units installed by the Ordnance Department. While the two concrete gun blocks were considered permanent, the battery was not provided with sewer, water, or commercial electric connection.(11) It is assumed that the two fixed guns were removed after the conclusion ofWorld War II in late 1945.

BC Land

Battery Land was provided with an improvised wooden fire control station (BC Land) at approxi­mately 140 feet elevation. The station was to be equipped with two M1910Al azimuth instruments, one Ml observation instrument, one M 1A2 height finder, and one M9A2 Director.(12) The battery was also provided with an SCR-593 radio.(13) The manning detail for this station was four personnel at all times.(1 4) A November 1945 reservation map shows BC Land constructed behind and to the rear of Gun No. 1 on the stubby ridge of Lands End proper.(15)

REPORT OF COMPLETED WORKS - SEACOAS (Gun Block)

Part VII Corrected to November 1943

Nii 2

ELEVATION

0

!! , ., "' ., ..... .., -"' a: . - N Oo •

~~ ....... ""'c'4.c .... ..,

✓

,"' e"

GUN BLQFK

...... ("" i ,

-­\ t I

.,/

,,

HARBOR DEFENSES OF SAN FRANCISCO LANDS END, CALIFORNIA 90 MM BATTERY N2 of Guns ~2 Caliber- 90 MM Carriage-T3-Fixed

20 0 20 40 60 eo FEET PLAN a ELEVATION

~ 0 ? IQ ll5 FEET

PLAN OF GUN BLOCK II SECTION

4)

lll

PLAN OF GUN BLOCK

I

· , · ,• 1_ 11 . • . · : • , I

_,,·· .-.. 1~11_ .• '. ,...-'-'-'< ~

!\!

FRANCISCO, CALIFORNIA

(:''.)

\ - - · ...

-~ ,:.) :_..

I - 16 - I

Fig. 5. Report of Completed Works (RCW) Part VII - 90 mm battery (Battery Land), Corrected to November 1943. NARA

~ l2'­~ "' ~ t:;-< <-, ~

"' (...:,

Sl "'

~ t, ~ ;:; ~ ~ ~

~ ;::, -

;;p ~ V'\ C<)

•. _.,.

PACIFIC OCEAN

--,"\ ,,,. ... ,...--= - - ----==-'"' -_.,/ .,.,_:;/'/ 55.35 ACRES - --:_-,_--:,-- --::;,;;:--=-=c-...-::::_ .

••-- F"'" ••• ,,, __ ,,,,;y _ ___..,,... -- '-·,. 40 MMAMTO '' IU-\E.DI ,;/ ~ . 511:0·0--•- ._5.~ .----...... '~ h.d: _.'! ' ___ ,,,,. - / ~-- • ,,,

-- - -.· .,,.,.,--', /-"-, ,,-,,-· ,,;Y ~-' --- ---· ... ,.- - - . - -- ' SL N! 22)(! ,, 0 - r r """ ,, -~· ,,;, "" =«r • . """"-•,, ;"',. ---..,, :!\ ____ .• .. -~,,__ _ __.,/- · -- . ,, '"' ''"'""'° <:>

J~

- ,, I . • ,._oo· -- . ,, i' ) 17;_ \\' \ -- i\!""":::-::. ::.;:-c-::.===-=---"' "-g-,;;,".:'-=-= ===-=--=---=--:..-:.-:_- •

¥ ) /;·. " . ' ·-, .. lo\~~-· -· ~"'- R!JC ':\~\' '•co, .. t;,..,------'-"",-,.-.=":~;,!;:;;::;,,-i ~- ~'I....--x Jr· ,,, • .• -~ --~- •• -ii~ , . . --

·"• ,oo ,1

I, .,; ' 1:, :: ,· '\ ~ - . '

P4RI(

I I ,!" Or iii ,~ ·= ' ·~ ,,..

''-- -==--::-::-::. -;.•'?

_-,:,: ;:;=::--. • '\__ so••><>'W ' _j' ,::::::::-;-- ---· 166 .w · - ·

' -l --· 200

FORT MILEY

ISEE EXHIBIT !!H-8}

SCAL E

zoo

FEET

4 0Q_

CONTOUR INTERVAL tS 10 fUT

600

RE VISED OAT

-- --~

• R OT

HDSF

Fig. 6. Government Leased Reservat ion Lands End - November 1945. NARA

NOTE

BEARINGS A.RE RUUIRED TO TRUE NORTH BASED ON RECORDE D DEEDS.

6 " LANDS EN D• ( U.S.E.O.)

LAT. 31'° 47' 16''.3'6 LOHG.122° 50' 167739

,_ •\: ·~ ,. ·~ I! I I

~

GOVER NMENT LEASED RESERVATION

LANDS END Loca1ion No. 18

HARBOR DEFENSES OF SAN FR AN CISCO IS NOVEMU:A 1945

V'.l

~ ~ "' -; I_\_)

2 Do

t;:l "' ~ i:, <.., ...,. t:, ~ ;:; <..,

"' ~ I:: -; ;:; i:, ......

~ ~ V\ \Q

Volume 32, Issue 3 The Coast Defense journal Page 60

Local Armament

The Lands End M.R. was defended by a single M2 .50-caliber antiaircraft machine gun behind Battery Land on the rock spine of Lands End. This gun position was identified as ".50-caliber Antiair­craft Gun No. 18."(16) There are no remains of this position at the reservation. (Fig. 6)

Additional Automatic _:w'eapons Positions

Authorization for four 37 mm batteries, each consisting of two M1A2 guns on M3 carriages, were allotted the harbor defenses of San Francisco for siting at Bonita Cove (south of Rodeo Ridge), Horse­shoe Bay, Fort Point, and Lands End by the 1st Indorsement, The Adjutant General's Office, file AG 660.2 (12-4-42) OB-S-E, dated 31 December 1942, to secret letter, Hq. Western Defense Command, file 660.2 HDSF(CA), to the Chief of Staff, War Department, dated 4 December 1942, Subject: "De­fense of Harbors Against Motor Torpedo Boats", ("Report on Defense Against Motor Torpedo Boats, Harbor Defenses of San Francisco," dated 15 November 1942). (17) -........_

40 mm guns were subsequently authorized in lieu of the 37 mm guns, allotted by the above cited references, by the 1st Indorsement, The Adjutant General's Office, file AG 472 (22 Aug 45) OB-S-E, dated 1 September 1945, to secret letter, Hq. Western Defense Command, file ARTY 660.2/37 HD Gen, to the Commanding General, Army Service Forces, dated 27 August 1945, Subject: "Replace­ment of 37mm AMTB Weapons."(18)

Bofors 40 mm Automatic Gun Ml

The Bofors 40 mm gun was an antiaircraft, multipurpose autocannon designed in the 193qs by the Swedish arms manufacture AB Bofors. It was one of the most popub.r antiaircraft systems during World War II, used by most of the western Allies. It remained in service as of 2013.

During World War II, Chrysler began mass production to supply the United States Army and Navy with the large number of 40 mm guns needed. Over the lifetime of the production, their en­gineers introduced numerous additional changes to make the manufacturing process more efficient, eventually reducing the overall time needed to build a gun by half.

In U.S. Army service, the single-mount Bofors was known as the 40 mm Automatic Gun M 1, on M2Al carriage. The U.S . version of the gun fired three variants of the British Mark II high explosive shell as well as the M81Al AP round, which was capable of penetrating some 50 mm of homogenous armor plate at a range of 500 yards.

Characteristics

The 40 mm automatic Gun Ml (AA) fired fixed AP and HE ammunition, 1.93 to 2.06-pound shells in rapid-fire bursts at a rate of 120 rounds per minute. The muzzle velocity was from 2,700 to 2,870 feet per second. The maximum effective range limited by the director was 3,000 yards. The gun was intended for duties intermediate between those of the high-altitude guns of the 3-inch and 90 mm class and the cal. 50 machine gun. It was effective against dive bombers and low-Hying aerial targets, and was also used against small boats and ground targets.(19) (Fig. 7)

Summer 2018

Weight of barrel assembly Weight of tipping parts Type of breechblock Primer mechanism

Bore: Caliber Length Length

Chamber: Length Taper Capacity

Rifling:

The Coast D efense j ournal

40 mm Automatic Gun Ml (AA)

295.85 lb. 1,05116. Vertical sliding wedge Percussion

40 mm (1.573 in.) 56.24 cal. ~8.58 in.

12.46 in. 0.051 per in. 29.9 cu in.

Length 75.85 in. Number of grooves 16 Depth of grooves 0.0225 in. Width of grooves 0.220 in.

Page 61

Increasing twist, from one turn in 45 calibers at the breech to one turn in 30 calibers at the muzzle.

Ammunition: Weight of complete round Weight of projectile Weight of propelling charge Length of complete round Type Muzzle velocity Time of flight at 1,500 yards

Range (maximum effective, limited by director)

Type of fire Rate of fire , rapid burst Capacity of magazine Capacity of cartridge clips Maximum recoil Elevation

4.58 to 4.82 lb. 1.96 to 2.06 lb. 0.65 to 0.7216. 12.60 to 17 .62 in. HE or AP 2,700 to 2,870 fps 2.0 sec.

3,000 yd. Single fire or automatic 120 rounds per min ? 'rounds 4 rounds 9.45 in -6° to 90° (20)

-•·

Volume 32, Issue 3 The Coast D efense journal Page 62

Battery Buck

In addition to the construction of Battery Land, a two-gun 40 mm AMTB battery was also estab­lished at the reservation in 1943. This temporary gun position was approximately 200 yards west of Battery Land, on the bluff overlooking Mile Rock Beach. (Fig. 8) Since the weapons emplaced were towed, site improvements would have been minimal and likely consisted of a prepared flat area along with earthen or sandbag revetments. No fortification construction except by troop labor was autho­rized for the 40 mm battery sites .(21) The battery was informally named "Battery Buck," after the

~ '::'reek of the commercial tanker SS Frank H Buck, .which ran aground on March 6, 1937, near Mile Rock Beach where the guns were emplaced. There are no remains of this temporary gun position.

In addition, 40 mm batteries were to be provided with improvised dug-in type magazines at each gun position during wartime for local ammunition storage.(22) It is unknown when the guns were removed; it is assumed that this occurred at the conclusion ofWorld War II in late 1945.

RA PD 71902

Fig. 7. 40 mm automatic gun Ml (AA) and 40 mm antiaircraft gun carriage M2 - firing position, low elevation. TM 9-252 (GPO, 1942)

Portable 60-inch Seacoast Searchlight

"'

Nine fixecf 60-inch searchlights and 26 portable 60-inch searchlights were approved as the project allowance for the Harbor Defenses of San Francisco, by the 3rd lndorsement, The Adjutant General's Office, file AG 660.2 (28 Jun 43) OB-S-E, dated 6 August 1943. The above allowance of thirty-five 60-inch searchlights included the four searchlights normally authorized the 90 mm AMTB batteries. (23)

In general, construction required fo r the tactical positions occupied by portable searchlights was provided by the post engineer and the troops manning the searchlights when the lights were in field positions. As all portable searchlights were in appropriate storage shelters at permanent reservations during peacetime, tactical position facili ties provided were temporary (either dug-in or surface wooden shelters) and intended to last only for the time the lights were in the field.

Summer 2018 1he Coast Defense j ournal Page 63

Fig. 8. Left to right - Battery Land and Battery Buck - Lands End- Image No. 201306182, September 27, 2013. California Coastal Records Project

Access roads, where required, were gravel-surfaced dirt roads.(24) Searchlight No. 22 was west of Lands End, on the bluff overlooking Mile Rock Beach at an elevation of 40 feet, at the Lands End M.R. The portable controller and power unit for this light was situated near the searchlight.(25) Noth­ing remains of this temporary searchlight position at the reservation.

Volume 32, Issue 3 The C,;,15t Defense journal Page 64

Tactical Organ..iLation and Assignment of Searchlights

Generally, searchlight direction was continuously maintained by the harbor defense command post. Specific searchlight direction and searchlight control was centralized in the highest command echelon that could observe the area involved. Searchlight direction or direction and control in each of the above was carried out through the searchlight officer. The tactical organization for Searchlight No. 22 was to be designated Lands End, under the general direction of the HDCP and under specific control of ATB-1, covering the beach areas along Lands End. (26)

60-inch Portable Se; rchlight Equipment

The searchlight sets authorized for issue to seacoast artillery units include the 60-inch mobile searchlight, the distant electric control station, the extended hand controller, the power plant, and interconnecting cables. Transportation was authorized separately on T/O&E.

Searchlight equipment in service included two types and several models. General Electric_,.and Sperry manufactured the equipment, each producing a new model each year between 1939 and 1942, designated by the number of the year (M1940, M1941, etc.), as well as two special models (M1941A and 1942A). Some earlier Sperry models dating as early as 1934 may still have been used during World War II. All of these items of equipment were originally designed for antiaircraft use but all could read­ily be used for seacoast artillery missions. (Figs. 9 & 1 O)

When issued, searchlights sets usually consisted of elements of the same type and model. However, with the exceptions of searchlights M1942 and M1942A, equipment made by the same manufacturer in different years differed so little as to be widely interchangeable. Control stations, extended hand controllers, and control cables of Sperry searchlights M1939, M1940, M.1941, and M1941A coul'd be used in any combination to operate any Sperry searchlight of those models. Control stations, extended hand controllers, and control cables of General Electric searchlights M 1940, M 1941, and M 194 lA could be used in any combination to operate any General Electric searchlight of those models. General Electric and Sperry power plants and power cables for 60-inch searchlights could be used with any type of searchlight of any model after 1936. Because of a modification in azimuth and elevation drive equipment, 1942 models of either type could not be used with control equipment of earlier models, but all components of General Electric and Sperry 1942 equipment were interchangeable except for the extended hand controllers.(27)

Searchlight Components

The seard'ilight consisted of the chassis, the base, the turntable (mounting the trunnion arms) , and the drum.

. 1. Chassis. The chassis, carried on four rubber-tired wheels, was primarily a frame for mounting the

searchlight. Four jacks, one at each corner of the frame, supported the equipment during operation and leveled the chassis. A towing bar was provided to move the searchlight by hand. The following equipment was mounted on the chassis: the dynamotor, which converted a portion of the D.C. supply into power for the A.C. elements of the equipment; the junction box, which contained receptacles for interconnecting cables; a ballast resistor, which compensated for varying lengths of power cable; and elements of the azimuth control system.

Summer 2018 1he Coast Defense journal Page 65

1. Ext ended hand control bar 11. Positive carbon. socket . 12. Lamp unit.

2. Arc a nd elevation control box. 13. Junction box. 3. Ventilating fa n motor. 14. Dynam otor. 4. Elevation zero reader. 15. Eleva tion scale. 5. Azimuth zero reader. 16. Azimuth scale. 6. Azimuth control box. 17. Front drum. 7. Ground glass finder . 18. Ammeter. 8. Lamp control box. 19. Voltmeter. 9. Peep sight glass. 20. Mirror.

10. Ballast resistor.

Fig. 9. General Electric M 1941 Searchlight. FM 4-175 ( 1942)

'---2. Base. The base assembly supported the turntable and transferred arc and control voltages to om-

er elements of the searchlight during operation. A central pivot and heavy-duty annular ball bearings supported the turntable. A slip-ring subassembly transmitted the required voltages from the junction box to brushes mounted on the turntable. An azimuth scale encircled the base. Searchlight azimuth circles were graduated in mils.

Volume 32, Issue 3 Ihe Coast D efense j ournal

17 :- -r

"-"---"'-~-...---... ~~ ---'---'----"-"---"

1. Azimuth d ata receiver hous­ing.

2. Lamp con trol m echanism box.

3 . Recarboning safety switch . 4 . Recarboning lamp switch. 5. Power cable receptacle. 6. Han d controller sock et. 7. Eleva t ion control m otor. 8. Elevation ze ro reader . 9 . Azimut h zero read er.

10. Arc view p eep sight.

11 . Ventilating motor. 12. Elevation scale. 13 . Ballast resistor. 14. Arc switch box. 15 . Azimut h sca le. 16. Junction box. 17. Front d ru m . 18. Lamp u n i t. 19 . Mirror . 20 . Ground glass finder. 21. Dyna m otor. 22. Eleva tion gear.sector.

Fig. 10. Sperry Searchlight Ml 941. FM 4-1 75 (1942)

Page 66

3. Turntable (trunnion arms). The turntable supported the drum at the trunnions and contained gearing which meshed with other gears on the base and the drum to move the searchlight in azimuth and elevation. All elevation control and drive mechanisms were mounted on the trunnion arms as­sembly.

The arc voltmeter, the arc ammeter, and the zero reading meters were also mounted on the trun­mon arms.

4. Drum. The drum was a large cylinder of aluminum alloy (or sheet steel, in some later models), consisting of front and rear sections joined to form a unit. It housed the lamp and the mirror. The lamp consisted of a high-intensity carbon arc and the necessary electrical and mechanical connec­tions to maintain a high current Row through the carbons and to keep the .gap separating them at a constant value. The composition of the carbons was such that the passage of a high current through chem and across the arc caused a small, brightly burning globule of incandescent gas to form at the tip of the posi tive carbon. This luminous ball of vapor was the light source for the searchlight. The 60-inch parabolic mirror focused light rays from the arc into a narrow (1 ¼ 0

) beam with an intensity of 800,000,000 candlepO\•.-er. ~-\ , ·entilacing fan, mounted on top of the drum, cooled the lamp elements and exhaust vapors gi,·en off b,· the arc, preventing discoloration of the mirror or the glass drum doors. Ocher conuol elemems :not:.med on the outside of the drum included: the lamp control mechanism,

Summer 2018 The Coast D efense journal Page 67

which controlled operation of the arc; the peep sights and ground-glass finder used to view the arc during operation; the elevation rack, which engaged the elevation drive gearing on the right trunnion arm; and a peep sight mounted on the left side of the drum used in orientation. The recarboning lamp, mounted inside the drum, provided light when it was necessary to change carbons during operation. An elevation scale was mounted on the elevation rack. (28)

Missions of Seacoast Searchlights

Seacoast artillery searchlights were employed primarily as a surveillance aid for coast artillery bat-teries and associated beach defense detachments. Searchlights were used to:

(1) Search water areas (searching lights). (2) Illuminate hostile naval vessels (illuminating lights). (3) Place a barrier beam across a channel or other confined approach to a defq 1ded area

(barrier lights). These lights were used only in exceptional cases. (4) Illuminate or search beaches.

Communications

CONTROL REMOTE CONTROL OF AZIMUTH 'AND ELEVATION

STATION ®- - __ - __ - __ - __ - __ - _ ,_A

0 CONTROL STATION BUZZER SIGNAL LINE TO LIGHT 0 OPERATOR SEARCHLIGHT 2 (MANS EXTENDED OPERATOR HAND CONTROL IN (MAINTENANCE EMERGENCY) TECHNICIAN)

iNTEi.LIG NC£ rA0M RA0AR

4TO OTHER

SLS

•

t LINES TO BATTERY ---- CP'S TO PERMIT ...---- CONTROL OF INDI· --a YIDUAL SL'S FROM

.,__ ____,. ANY BATTERY.

t::::\ LIGHT OcoMMANDER

POWER Pt.ANT

0 POWER PLANT OPERATOR r - - - - T;U,;;S - - - ~ - - 1

: SWITCHBOARD SWITCHBOARD OSWB ~ RELOCATING CHART FOR (COMMAND POST) (SEARCHLIGHT) OP Fi USE WHEN SURVEILLANCE

I l: . I RADAR IS SUPPLYING TAR· I t;;;\SEARCHLIGHT I GET POSITION DATA . I · 0 OFF~ER

LCOMM~D_!O!,T - - - - - - - - - - - _J MAP . . (OPERATIONS- SITUATION)

Fig. 11. Searchlight communications schematic. FM 4-29, ( GPO, 1945) . A telephone net suitable for use by both harbor defense units and mobile organizations is shown

in Figure 11. This installation could be modified to place the searchlight officer and the searchlight switchboard in the radar station where this was practicable. However, it was of primary importance for the searchlight officer to have an uninterrupted view of the water area covered by the searchlights under his control. ·Tue circuit from the searchlight switchboard to the telephones at the searchlight and controller should be operated as a "hot loop," that is, one or both of the telephones should be manned at all times except when the command REST had been given. When the searchlight squad was

Volume 32, Issue 3 The Coast Defense j ournal Page 68

at rest, one or more members of the squad would be near enough to the telephone at all times to hear the ringing signal. When the tactical si tuation required control of any searchlight or searchlights be turned over to the commander of a firing battery, the battery CP and searchlight or searchlights should be connected through the searchlight switchboard as indicated. This net might be readily modified in situations requiring additional lines (as in the case of a 155 mm battalion operating as four two-gun firing units). The searchlight officer's telephone could be eliminated; if so, the officer relayed his com­mands to the searchlight squads through the telephone operator. The trunks between the command post switchboard and the searchlight switchboard could be eliminated if the two switchboards were

~ dose enough together to permit direct oral relay of intelligence between the two switchboards. Two or more searchlights could be connected on a single line. In this case, searchlights sited to illuminate the field of fire of a particular battery or firing unit should be connected on the same line to facilitate searchlight control by the battery commander. If necessary, the battery searchlight control line may have been connected through the command post switchboard. In this case, trunks connecting the command post switchboard and the searchlight switchboard would be necessary. "

Assignment and Pickup of Targets

When the searchlight officer desired to illuminate a target located by surveillance radar or other means, he telephoned a relocated azimuth to the searchlight or searchlights best able to illuminate the area, allowing for travel during 20 seconds of dead time. If the target was not illuminated when the searchlight was turned on and was not detected in the 10° sector of search, the searchlight officer gave the orders necessary to place the searchlight beam on target. He commanded: RAISE (or LOWER) if it was evident that the range of illuminated area was widely different from the range of the target.,If it was apparent that an error had been made in azimuth, he commanded: SEARCH RIGHT (or LEFT) . If one searchlight of several assigned to a target picked it up, the searchlight officer commanded: COVER, thus indicating that the other lights are to cover the illuminated target. If the nature of the error was doubtful, he ordered one searchlight to search the area in which the target was believed to be. He directed the other searchlights: OUT, prior to the investigation of the error. When the target had been picked up, the searchlights were assigned to track it in accordance with the principles set forth in FM 4-5.

Assignment and Pickup of Motor Torpedo Boat Targets

During the searching phase, the searchlight assigned to the AMTB battery might be controlled by the searchlight officer as described above. When a particular target was to be engaged by the AMTB battery, contr~l of the AMTB searchlight was exercised by the battery commander.

(1) Position data fo r poiming the AMTB searchlight was obtained initially from higher headquar­ters (surveillance radar). If control was relinquished to the battery commander before the light was put in action, position data would be determined during the interval by the radar set assigned to the battery.

(2) Because of the speed and maneuverability expected of motor torpedo boats, elapsed time be­tween the assignmem of cargecs and the turning on of the searchlight was kept to a minimum. When­ever mo tor torpedo boatS were dececced in the area covered by the harbor defense radar, the AMTB searchlight was ordered ro ST.-\..."D BY with power on and the DEC system oriented and synchro­nized. \\"hen it beca..."":le apparent chat a target being tracked by radar was following a course which might bring it imo &'le Sa.~e~··s field of fire, azimuths determined by radar and relocated on a board

Summer201 8 1he Coast Defense j ournal Page 69

in the BC station would be relayed to the searchlight at frequent intervals. Each time, the searchlight would be traversed to the indicated azimuth by distant electric control. The light commander would check each time to ee that the proper reading appeared on the azimuth scale at the searchlight. When it was desired to place the light in action, the battery commander commanded: IN AZIMUTH (relo­cated azimuth with no allowance for dead time).

(3) The searchlight beam was to be spread at the order of the battery commander for illumina­tion of motor torpedo boat targets at ranges less than 5,000 yards. In addition to facilitating the task of tracking high-speed, maneuvering targets, the added beam width compensated for errors in radar azimuth data and for any possible delay in relaying data from the radar station to the searchlight. (29)

Cable Hut

A dug-in reinforced fire control communications cable hut was also built on the reservation be­tween 1943 and 1945. This structure was identified as the Lands End - Scott - Barry Cable Manhole. When this hut was transferred for use by the coast artillery troops is not known. There are no remains of this structure on the reservation.

Post War Use

With the expiration of the lease of the 55.35 acres of land forming Government Leased Reserva­tion Lands End on June 10, 1945, and the conclusion ofWorld War II a few months later, Lands End M.R. with its two batteries, searchlight, and cable hut was no longer needed.(30) By 1951, the army relinquished control of the Lands End area and returned the 55.35 acres of land back to the City and County of San Francisco for their use. (31)

The Lands End Military Reservation in 2017

The site was inspected by the author on March 14, 2017. The former reservation can easily be ac­cessed by parking or walking from the El Camino Del Mar parking lot behind the Palace of the Le2'ion of Honor and making ones way through the Lincoln Park Municipal Golf Course to the Coastal Trail. connecting finally with the Mile Rock Lookout Trail at Lands End. As of March 201 7, the only un-iY­ing elements for Battery Land at the very tip of Lands End are the two concrete 90 mm gun blo · . Both gun blocks still retain the steel mounting bolts set into the concrete bolt circles. (Figs. 12 13 AQy traces of the temporary dug-in magazines, improvised wooden fire control station, and any up­port buildings that may have been built by the gun crews have vanished over time. There are howeYer. the remains of a collapsed corrugated metal structure dug into the rocky ridge between the two gun blocks that may have served as a ready room for the gun crews or an ammunition shelter for the 90 mm or .50-caliber machine guns, (Fig. 14) and the remains of a concrete cable vault behind the rocky ridge at Lands End. (Figs . 15 & 16) The only other surviving element at Lands End is the access road to the battery that was likely widened and improved by the army.

As of March 201 7 , there are currently no remains of the site for Battery Buck, which more than likely consisted of a prepared flat area with earthen or sandbag revetments, and no remains of the posi­tion for Searchlight No. 22, which was situated approximately 50 feet west of the two 40 mm AMTB guns. The Lands End - Scott - Barry Cable Manhole located near the beginning of the Coastal Trail at the Eagle's Point Overlook adjacent to the 17rh hole at the Lincoln Park Municipal Golf Course, no longer remains.

Volume 32, Issue J The CtJast D efense j ournal Page 70

Battery Land serYes as che only surviving example of a 90 mm AMTB battery constructed during World War II within HDSF co haYe boch concrete gun blocks fully exposed. This banery is also unique due to its location commanding the Golden Gate Strait some 85 feet above sea level, and the visible remaining concrete sandbags that formed a temporary structure behind the battery. While three 90 mm batteries were constructed for the harbor defenses of San Francisco, Battery Land stands alone as a prime example of World War II-era AMTB battery construction.

Fig. 12. Concrete gun block for Gun No. 1, Battery Land. Photograph by author, March 201 7.

Fig. 13. Concrete gun block fa: Gun ~ o. 2, Battery Land. Photograph by author, March 2017.

Summer 2018 The Coast D efense j ournal Page 71

Fig. 14. Concrete sandbag remains of the collapsed corrugated metal structure located behind Battery Land. Photograph by author, March 201 7.

Fig. 15. Concrete cable Ya ult behin e rocky ridge of Lands End. Photograph by author, March 201 7.

--.•-

Volume 32, Issue 3 7he Coast D efense j ournal Page 72

Fig. 16. Surviving cable duct openings to the cable vault. Photograph by author, March 2017.

Endnotes

1. War Department, "Supplement to Harbor Defense Project, Harbor Defenses of San Francisco, 15 November 1945," Section III, Miscellaneous, pp. 45-47, NARA, College Park, MD, RG 407, Entry 366.

2. Ibid., p. 20.

3. Mark A. Berhow (ed.), American Seacoast Defenses, A Reference Guide, 2nd Ed. , (McLean Virginia: CDSG Press, 2004), pp. 249-250.

4 . War Department, Coast Artillery Training Bulletin, Vol. 2, No. 16, 90-mm Gun Fixed Mount Service of the Piece (Tentative Field Manual FM 4-91), July 1943, Coast Artillery School, pp. 3-6.

5. War Department, Technical Manual TM 9-373, 90-MM Gun Ml and 9 0-mm Gun Mount T3 (GPO, March 1943\ pp. 8-9.

6. War Department, RCW - Seacoast Fortifications, Parr 1, Battery Lands End, corrected to October 1943, and Gun Block, Parr VII, 90 MM Battery, corrected to November 1943, NARA, College Park, MD, RG 77, Entry 1007.

7. Ibid. (Note: According to the "Armament Data - Harbor Defenses of San Francisco," the guns listed are serial numbers 7189 and 7083, both manufactured by Chevrolet Motors Co. The carriage numbers and manufactures are the same.)

8. ''Armament Data - Harbor Defenses of San Francisco," NARA, College Park, MD, RG 165, Entry 257, Box 68.

9. War Department, ~Supplement to Harbor Defense Project, Harbor Defenses of San Francisco," p. 23.

10. Ibid., p. 24.

11. \'.(far Deparrmem. RC\\- - Seacoast Fortifications, Part 1, Battery Lands End.

Summer2018 Ii:e Coast Defense journal Page 73

12. War Deparrment. - -?? mea~ ro Harbor Defense Project, Harbor Defenses of San Francisco, 15 November 1945," Annex B. Fire Co -rol. pp. 1-42, ARA, College Park, MD, RG 407, Entry 366.

13. Ibid., p. 27.

14. Ibid.,p. 41.

15. War Department. - upplement rn Harbor Defense Project, Harbor Defenses of San Francisco, 15 ov 194 - ;· Section III , Miscellaneous, . ·umber 6-A, Locations of Army Controlled Land, Exhibit 56-B, Government Leased Reservation Lands End.

16. Ibid., Annex E, Amiaircraft Anillery (HD), p. 9.

17. Ibid., pp. 20-21.

18. Ibid., p. 21.

19. War Department, TM 9-252, Bofors 40-mm Automatic Gun Ml and 40-mm Antiaircraft Gun Carriages -~ '2 -,u;

M2Al Technical Manual, Periscope Film LLC, 2013, pp. 5, 8.

20. Ibid., pp. 12-1 3.

2 1. War Department, "Supplement to Harbor Defense Project, Harbor Defenses of San Franci co, 1 · . ·ovembe 1945," Section III , Miscellaneous, pp. 22-23.

22. Ibid., p. 24.

23 . Ibid., Section C, Seacoast Searchlights, p. 6.

24. Ibid., p. 9.

25. Ibid., p. 7.

26. Ibid., p. 2 & 4.

27. War Department, Coast Artillery Field Manual FM 4-29, Service of Seacoast Searchlight (The Army Field Printing Plant, Fort Monroe, Va., 30 August 1945), pp. 5-8.

28. Ibid., pp. 8-10.

29. Ibid., pp. 20 & 21, 23 & 24.

30. War Department, "Supplement to Harbor Defense Project, H arbor Defenses of San Francisco, 15 November 1945," Section III, Miscellaneous, pp. 45-47.

31. John Martini, "Merrie Way & the Lands End Street Railways Abbreviated Cultural Landscape Report" (San Francisco: Golden Gate National Recreation Area, January 2006), p. 93.