Self-determination—the idea that the citizens of a nation should decide (“determine”) what the government of that nation should be—this is not the same as democracy if the citizens want a monarchy or dictatorship, for example
Mandates—former Central Power territory that was commanded over (“mandated”) to Allied Powers after World War I
League of Nations—an international organization that settles disputes between countries (the predecessor to the current United Nations)
Couldn’t the Allied Powers have foreseen the unsatisfied interests of some countries (Italy, Japan) and the desire of Germany to seek revenge after its humiliation, and known that this might lead to another war? Were they just too confident of their own abilities or did they think another war might lead to more profit?