To decide whether a utilitarian would justify a war we would have to consider the circumstances surrounding the war and the consequences of going to war, looking at what the greatest amount of good for the greatest amount of people would be.

A utilitarian may justify going to war to get rid of an evil dictator in a society who was abusing the human rights of civilians. This action would result in the greatest amount of happiness for the greatest amount of people which from a utilitarian viewpoint would make war under this circumstance morally permissible. A relevant example can be found in WW2, it could be argued from a utilitarian standpoint that this war was morally justifiable because removing Hitler created happiness, not only within his own country (and the surrounding areas) where human rights abuses were visible in the form of Jewish persecution, but also around the world as it would end the war and soldiers could return to there loved ones which would generate happiness. It seems that the consequences of going to war would lead to more happiness than not going to war.

Furthermore, a utilitarian may justify a war because in the long term war may create peace, which would generate the most amount of happiness on a global scale.

On the other hand, the money spent on war may be better used on providing the basics for everyone e.g. shelter, healthcare food and clean water. Which could produce more happiness for a greater amount of people. Therefore on these grounds a utilitarian may not believe that war is morally justifiable. To illustrate further, some of the poorest countries in Africa spend two or three times as much on armaments as they do on health. Those who suffer from illness cannot be treated because of a shortage of funds for health care. From a utilitarian viewpoint war in this instance is not generating the most amount of happiness, it is creating more pain.

However, it could be argued that the suffering of those in the country under the rule of a dictator, for example, may outweigh the suffering of those who need medical assistance and therefore if war was started to remove the dictator there would be more happiness generated than if the country had used the money on the health system.

A utilitarian may not believe war is morally justifiable because they may not want to be drawn into conflicts where you are supporting your allies. They may find it more realistic to look after the happiness of people in their own country rather than on a global scale. So being drawn into a war because of the alliance your country has is unrealistic if you are only concerned about the happiness of those in the country you inhabit. This is because there would be economic and environmental costs of war in your country creating pain and suffering not happiness, not to mention the lives lost and the injuries both in the long term and short term which would be sustained.

It can also be observed by looking at the past that violence leads to more violence, this is evident in modern times within the Israeli and Palestinian conflict, when there is a ceasefire a violent act breaks it which erupts into more violence. These constant acts of violence are not in the interests of the majority a utilitarian could argue, therefore on this ground they would believe war is not justifiable.