Hitler's troops marching into the Rhineland, 1936. Defying the post WW I. treaty, the Rhineland part of Germany was to have been occupied by the Allies for fifteen years.
World War 2 might have been able to have been stopped then and there. I guess we will never know if that was possible.
The treaty of Versailles was signed in 1919 and ratified in 1920 so the 15 year occupation was actually up in 1935. In practice though the allies had pulled out by 1930 and never exercised their right under the terms of the treaty to re-occupy it at will.
Hitler and his ‘staff’ chose a very good time to occupy as with their weak Army of the time they could not have done much. France was holding elections and the British who had never fully backed the French demands at Versailles, considered it nothing to do with them.
Hitler for all his gross errors was a very good bluffing others. Has anyone heard if Hitler was any good at poker?