WWII is a bad example.

Hitler was doing pretty well for himself (and managed to get the army doing amazing things) until people began intervening. France just laid down for them, as did Poland, and Austria, and Czech Republic...but then again, much of that was due to the Blitzkrieg tactics.

Russia managed to beat the Germans with their weather. And all the Allies brought an end to the Tyrany.

Most of the war was fought by politicians doing things, and it all turned out right in the end.

I'd say a good example would be the Vietnam war, with Nixon (was it?). But then again I'm no great for American history.