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He joined the Wehrmacht in the autumn of 1938 and belonged to the Potsdam Infantry Regiment 9. At the Battle of Stalingrad, he was badly wounded and in 1943, he was posted to the indoor service, that is to say, an office, at the Oberkommando der Wehrmacht. He was drawn into the plan to assassinate Hitler by Fritz-Dietlof von der Schulenburg.
On 11 July 1944, on the first attempt on Hitler's life, Klausing went along with Claus Schenk von Stauffenberg as his adjutant to the Obersalzberg (i.e. the Berghof near Berchtesgaden) and made sure that a car and a plane were standing by, ready to whisk the plotters away to Berlin after the job had been done. The Obersalzberg plan was, however, put off, as was a second attempt on 15 July at the Wolf's Lair near Rastenburg in East Prussia, where Klausing made the same preparations for Stauffenberg.
On 20 July, Captain Klausing stayed behind at the Bendlerblock in Berlin while Stauffenberg went to the Wolf's Lair to try again, and was jointly responsible for forwarding Operation Valkyrie orders. He forwarded the orders to, among others, Ewald-Heinrich von Kleist-Schmenzin. On the night of 20–21 July, after it had become apparent that Stauffenberg's briefcase bomb had not killed Hitler, Klausing was the only one to escape the firefight at the Bendlerblock subsequent to which Stauffenberg and several other conspirators were captured, but the next morning, he gave himself up to the Gestapo.
- "MEN TRIED SWIFTLY: Plotters Executed Two Hours After Sentence by 'People's Court' MARSHAL TOPS LIST Himmler Death Rumor, Wounding of Goering Are Unconfirmed 8 GERMAN OFFICERS HANGED FOR PLOT". The New York Times (ProQuest document ID 106962698). 9 August 1944. p. 1.