We'll never know. But if he had died in WW1, He never would have met the National Socialist Worker's party.

They met in the back of an old pub that stank of cat piss, according to Hitler. There were many such political clubs, and Hitler wanted to get into politics. These guys were not terribly motivated before Hitler showed up. He became member number 7, I think.

Without him, they would not have had his magic oratory ability, which he discovered to his own surprise when he started giving speeches. They would also not have his drive, his fire, and his ruthlessness.

So maybe no Nazis. No war, though? Is history driven by the actions of men, or by the impersonal forces of demographics and economics?

That is history's great debate.