In mid 1943, Thiele declined a posting to No. 617 Squadron under the command of Guy Gibson, the man who had led that squadron on the May 1943 Dambusters raid that blew up the Ruhr dams. A few weeks after the raid, Thiele received a message that Gibson wanted to see him at RAF Scampton, in Lincolnshire. Thiele, with 50 operations behind him, told Gibson that he had had his fill of bombers and was desperate to fulfil his ambition to fly Spitfires. He informed Gibson that he did not want to appear ungrateful but disclosed he already had the wheels rolling to go to a unit flying experimental Spitfires as a step out of Bomber Command. Thiele believed that he had been picked out by Ralph Cochrane of Group Headquarters as a likely successor to Gibson, a position that would eventually go to Squadron Leader George Holden. Thiele's decision not to join No. 617 Squadron proved the right decision. On the night of 15–16 September 1943, 5 of the 12 Lancasters were lost during a mission to bomb on the Dortmund-Ems Canal, including Holden's, which was shot down by flak with no survivors.