In 1936, Hitler's forces crossed the Hohenzollern Bridge and entered the demilitarised Rhineland at Cologne.
It was a bluff which Hitler freely admitted on a later occasion:
"If the French had marched into the Rhineland, we would have had to withdraw with our tails between our legs."
However, unchallenged, the Germans stole land denied to them back in 1919 with forces he was not allowed to keep and which were virtually ignored by all of the pathetic countries of The League of Nations.
The French did not have the guts.
The British no longer had sufficient armed forces.
Had Hitler been challenged at this point and if the Treaty of Versailles had been acted upon - THERE WOULD HAVE BEEN NO SECOND WORLD WAR IN EUROPE!
Weakness always carries a heavy price, whether dealing with criminals or rogue nations