On 11 March 1938, Hitler sent to Vienna the ultimatum precipitating the Anschluss. On the 12th, the German army marched in. On the 13th, the annexation of Austria to Germany was proclaimed.

Naturally, this development posed the question, as everyone understood, of the fate of the Sudetenland. In a move typical of Hitler's foreign policy – dishonest, deceptive, yet for a long time credible to the credulous – Field Marshal Göring contacted the Czechoslovak minister in Berlin and “gave [Vojtěch] Mastný his word of honor that the entry of German troops into Austria had been ‘nothing more than a family affair’ and that Germany was disposed to maintain her former policy of mutual improvement of relations with Czechoslovakia,” as a proof of which, Prague was informed, the German army had been given strict orders not to approach closer than fifteen kilometers to the Czechoslovak frontier. The Hungarian ambassador in Berlin, Döme Sztójay, witnessed Göring repeat the statement to Mastný three times. In private, on the other hand, in the absence of Mastný, when Sztójay raised the question of Czechoslovakia, Göring revealed a different plan: “At the present time, it is a question of arranging the affair of Austria, and subsequently the turn of Czechoslovakia will certainly come.” He emphasized that “the preparations were not yet sufficiently advanced to be able to unleash an attack that would require considerable forces.” Göring's statement of reassurance, however, was given wide circulation by both the Germans and the Czechoslovaks.