Why do wars start?

War usually starts because of technical problems and some countries teaming up to fight one country to another, sometimes the problem Why war starts is because they need things that also the other countries need, Ex. Countries need food or water like people. and they might take over of the country that they are trying to evade... or even try to gain the country themselves, the country that evaded for example. America and Asia, they fight the Philippines and Philippines won... for some reason and when Philippines won Philippines evades more countries. some kind of like that