Rhineland
Back when the Treaty of Versailles ended WWII one agreement by Germany was that there would be a demilitarized or buffer zone between itself and france to try and prevent a conflict. hitler's reasons were that france was weakened because the government was losing power and a temporary government was currently in charge, it would boost natzi popularity, Britan was too busy dealing with italy and its invasion of ethiopia, and also because Hitler did not want to wait any longer. on March 7th 1936 Germany marched into the Rhineland and militarized the french border which sent alarm bells throughout France and Britain. France then mobilized its military but did not have Germany back down even though germany would have because of france's military strength at the time.