Machinations by the SD, the Gestapo, and the SS helped to bring Austria fully into Hitler's grasp and on 13 March 1938, he signed into law the union with Austria as tears streamed down his face. "Case Green" and the Sudetenland Concomitant to its machinations against Austria, the SD also became involved in subversive activities throughout Czechoslovakia. Focusing on the Sudetenland with its 3 million ethnic Germans and the disharmony there which the Czech government could not seem to remedy, Hitler set Heydrich's SD in motion in what came to be known as "Case Green". Passed off as a mission to liberate Sudeten Germans from alleged Czech persecution, Case Green was in fact a contingency plan to outright invade and destroy the country, as Hitler intended to "wipe Czechoslovakia off the map." This operation was akin to earlier SD efforts in Austria; however, unlike Austria, the Czechs fielded their own Secret Service, against which Heydrich had to contend. Once "Case Green" began, Heydrich's SD spies began covertly gathering intelligence, even going so far as having SD agents use their spouses and children in the cover scheme. The operation covered every conceivable type of intelligence data, using a myriad of cameras and photographic equipment, focusing efforts on important strategic locations like government buildings, police stations, postal services, public utilities, logistical routes, and above all, airfields. Hitler worked out a sophisticated plan to acquire the Sudetenland, including manipulating Slovak nationalists to vie for independence and the suppression of this movement by the Czech government. Under directions from Heydrich, SD operative Alfred Naujocks was re-activated to engage in sabotage activities designed to incite a response from the Slovaks and the Czechs, a mission that ultimately failed. In June 1938 a directive from the SD head office indicated that Hitler issued an order at Jueterbog to his generals to prepare for the invasion of Czechoslovakia. To hasten a presumed heavy response from the French, British, and Czechs, Hitler then upped the stakes and claimed that the Czechs were slaughtering Sudeten Germans. He demanded the unconditional and prompt cession of the Sudetenland to Germany in order to secure the safety of endangered ethnic Germans. Around this time, early plots by select members of the German General Staff emerged, plans which included ridding themselves of Hitler. Eventually a diplomatic showdown pitting Hitler against the governments of Czechoslovakia, Great Britain, and France, whose tepid reaction to the