There is a thing called peace without justice. It happens at the end of every war, even those that end in unconditional surrender.

Justice is subjective. One war ends. The winners see justice. The losers sees injustice.

I don't know if you're a history buff, but about 100 years ago there was a really big war. The losers of that war (known as WWI) went on 25 years later to start another war (aka WWII) to address the injustices they felt from the end of the prevous war. Of course there were other justifications given for the next war, but injustice from the last war was the first and most potent reason.

BTW: You might want to look up the definition of "proxy war."