War benefits the government of Oceania and other superstates by providing a continual excuse and rallying point. That is to say, the government could always justify any sort of action, no matter how despicable, through claims that a war was going on. Likewise, it was a way to justify economic rationing. War is a way to channel emotion, as in Hate Week, and if you're at war, it is always the case that you have enemies. This allows an ongoing excuse for searching for enemies of the Party. This in turn emphasizes loyalty and reduces critical thinking.