What happened after Hitler invaded the Rhineland?
Nothing. The Allied powers of France and England did not respond militarily to the movement of German forces into the Rhineland
The re-militarization of the Rhineland was a violation of the Treaty of Versailles ending world war I. The league of nations (formed by the same treaty) condemned the occupation of the Rhineland by German forces but nothing was done. The armies of Germany were not ready to fight a major campaign at the time of the militarization of the Rhineland. The well armed French army could have destroyed the new German forces. But neither the French or the British wanted to fight another war against Germany, so nothing happened.
The Rhineland had been part of Germany before the defeat of world war I. The Rhineland with its coal and industry might have been taken away from Germany to prevent it from becoming strong enough militarily to again threaten France. The Western Allies allowed Germany to re-militarize this territory rather than fight another war.
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Hitler did not invade the Rhineland, which was already German land, but he took a gamble and restored military personnel and started an arms buildup in the forbidden territory.
The Rhineland was a part of Germany that was supposed to be free of military personnel or equipment to ensure the safety of the border countries of France, Belgium and Holland. Germany was also required to limit her army to 100,000 men 36 ships to which the Germans strongly objected. Germany agreed to the terms of the Treaty of Versailles by signing the Treaty of Locarno in the 1920’s.
After Adolf Hitler became Chancellor of Germany he vowed to pull out of the Treaties and return troops to the Rhineland. To increase her security, France signed a treaty with the USSR, which Germany used to reason their movement of military personnel back into the Rhineland.
The British did meet with the Germans at this point, since both treaties had been ignored. France was now heading to a general election, and the British people felt the Treaty of Versailles was not fair to the German people.
As a result, Britain did nothing about the German aggression and France was tied down. Hitler then proceeded to occupy Austria and the Sudetenland, Czechoslovakia, then on to Poland.