Except when they don’t. We are living in The Long Peace. A period since 1945 where no two major world powers have gone to direct combat with each other. Longest time in history. And there is always a new Hitler, Stalin, etc in each generation. America’s vast military superiority has played a major role in this period, to deter a-holes with certain death. But that does not deter the mentally unbalanced - jihadists, etc, who believe their actions guarantee heaven. You are right, except for the times in history that you are wrong.