the German Staff College in 1935, Gehlen was promoted to captain and assigned to the German General Staff. Gehlen served on the General Staff until 1936 and was promoted to major in 1939. Second World War At the time of the German attack on Poland (1 September 1939), he was a staff officer in an infantry division. In 1940, he became liaison officer to Field Marshal Walther von Brauchitsch, Army Commander-in-Chief; and later was transferred to the staff of General Franz Halder, the Chief of the German General Staff. In July 1941, he received a promotion to lieutenant-colonel and was sent to the Eastern Front, where he was assigned as senior intelligence-officer to the Fremde Heere Ost (FHO) section of the Staff. Head of FHO In spring of 1942, Gehlen assumed command of the Fremde Heere Ost (FHO) from Colonel Eberhard Kinzel. Before the Wehrmacht disasters in the Battle of Stalingrad (23 August 1942 – 2 February 1943), a year into the German war against the Soviet Union, Gehlen understood that the FHO required fundamental re-organisation, and secured a staff of army linguists and geographers, anthropologists, lawyers, and junior military officers who would improve the FHO as a military-intelligence organisation despite the Nazi ideology of Slavic inferiority. Hitler assassination plot, 1944 In summer 1944, German Resistance leaders Colonel Henning von Tresckow, Colonel Claus von Stauffenberg, and General Adolf Heusinger recruited Gehlen into participate in their 20 July plot to assassinate Adolf Hitler and overthrow the Nazi Party. As head of the FHO, Gehlen allowed the military conspirators to make their plans under his protection, and he was present at their meetings at Berchtesgaden. However, after the assassination attempt and subsequent coup d'etat failed on 20 July 1944, he escaped falling victim to Hitler's 4,500 revenge killings. Dismissal, 1945 Gehlen's cadre of FHO intelligence-officers produced accurate field-intelligence about the Red Army that frequently contradicted rear-echelon perceptions of the eastern battle front. Hitler dismissed the gathered information as defeatism and philosophically harmful to the Nazi cause against "Judeo-Bolshevism" in Russia. In April 1945, despite the accuracy of the intelligence, Hitler dismissed Gehlen, soon after his promotion to major general. Preparation for Post-War The FHO collection of both military and political intelligence from captured Red Army soldiers assured Gehlen's post–WWII survival as a Western anticommunist spymaster, with networks of spies and secret agents in the countries of Soviet-occupied Europe. During the German war