Of course there were atrocities by the other side, no one said there weren't. However, I was speaking of the post-war actions of the victors. When you win, you get your revenge or justification by winning. When you lose, you just feel resentful you lost, and wait until you have another chance, perpetuating the cycle of war.

In the case of WWII, a concerted effort was made by the victors to make peace with the losers -- subverting the "we'll get them next time" syndrome.