It’s possible World War II (and the Vietnam War) may have been averted if the Allies had not implemented the “Treaty of Versailles”. One of the priorities of the Treaty was to prevent conditions that led to World War I from ever happening again. One way the Treaty did this was to impose harsh sanctions on the Central Powers, especially Germany.
Germany was forced to accept responsibility for the war and to pay reparations for costs. Germany’s economy had already been stretched to the limits during the war. Having to pay reparations on top of an already decimated economy led to an economic depression in Germany, which led to the rise of Hitler, and to the Second World War.