The Treaty of Versailles is what gave rise to Hitler. Had the League of Nations not be determined to break the German people for their crime of WWI, the German people would probably have not been embittered to do WWII.
It was even before that. Even in WWI, Germany was reluctant to fight. They had a strong economy and the bloodthirsty central bankers (You know who) wanted a piece of it.
They were clearly winning until the you-know-whos got the U.S. involved.
WWI was nothing more than a pissing contest among dying empires. If the U.S. hadn't got involved, it would have ended in a stalemate (Similiar to the War of 1812) and Europe would have been stronger and the 20th century would have been much different.