How did World War 1 lay the foundation for World War 2?

WWI was a basis for WWII in part because of the Treaty of Versailles. This treaty was harsh toward the Germans. They resented it. Hitler, as Germany's Chancellor, broke all the points in the treaty.

Everyone disliked Germany because of WW1. In Germany there arose a conspiracy theory that claimed that the country had been 'betrayed' by Communists and the Jews. This 'stab-in-the-back' legend was used by German nationalists and the German military to cover up their failure. Hitler used this conspiracy to destabilize the new republic.