On 8 August 1940, Köstring was warned by General Franz Halder that "he would have to answer a lot of questions soon",[1] making him one of a few people who knew what would happen with Russia despite the non-aggression pact. With the planned Operation Barbarossa his position in Moscow was untenable; he was repatriated under diplomatic immunity and assigned to the Führerreserve. He visited, together with Friedrich Werner von Schulenburg, prisoner of war camps recruiting Soviet POWs for the German war effort.