Under the terms of Versailles, the Rhineland had been made into a demilitarised zone. Germany had political control of this area, but she was not allowed to put any troops into it. Therefore, many Germans concluded that they did not actually fully control the area despite it being in Germany itself.
In March 1936, Hitler took what for him was a huge gamble - he ordered that his troops should openly re-enter the Rhineland thus breaking the terms of Versailles once again. He did order his generals that the military should retreat out of the Rhineland if the French showed the slightest hint of making a military stand against him. This did not occur. Over 32,000 soldiers and armed policemen crossed into the Rhineland
Why didnít the Allies (Britain and France) do anything about this violation of the Versailles Treaty ?
France was going through an internal political crisis at the time and there was no political leadership to concentrate against Nazi Germany. Britain generally supported the view that Nazi Germany was only going into her own "backyard" and that this section of Versailles was not needed to be enforced in the mid-1930ís. It was believed that Germany was behaving in a reasonable and understandable manner.
Hitler learned from this episode that he could all but gamble on France not doing anything. The Rhineland affected the French in that a demilitarised Rhineland was created at Versailles to act as a barrier for the French if the Germans ever got war-like again. It appeared that in 1936 that France was not even willing to fight for this. Therefore, Hitler concluded that it he turned his attentions to the east of Europe, France would be even less willing to involve herself. From the British point of view, Hitler concluded that there was room for movement with regards to Versailles as the media, in some areas, had made it clear that they believed that some of the terms of Versailles were not appropriate for the 1930ís.
"Rhineland 1936". HistoryLearningSite.co.uk. 2005. Web.