When Hitler and his army chiefs asked for a pretext for the invasion of Poland in 1939, Himmler, Heydrich, and Müller masterminded and carried out a false flag project code-named Operation Himmler. During one of the operations, the clandestine mission to a German radio station on the Polish border, Müller helped collect a dozen or so condemned men from camps, who were then dressed in Polish uniforms. In exchange for their participation, the men were told by Müller that "they would be pardoned and released." Instead, the men were given a lethal injection and gunshot wounds to make them appear to have been killed in action during a fake attack. These incidents (particularly the staged attack on the Gleiwitz radio station) were then used in Nazi propaganda to justify the invasion of Poland, the opening event of World War II.