1940 with sorties over Norway and over the Ruhr. In July 1940, No. 10 Sqn were transferred to RAF Leeming when it was opened, with an administrative detachment from No. 78 Sqn sent to Leeming as well to get the base up and running. Dishforth was used by several squadrons from RAF Leeming during early 1941 for '"bombing-up purposes", as the airfield at Leeming was in the process of being concreted. Later in 1940, No. 78 Sqn returned from Leeming, with No. 10 Sqn being posted out of Dishforth for Leeming, leaving No. 51 and No. 78 Sqns at Dishforth. In February 1941, Whitleys from both squadrons took part in Operation Colossus, a commando raid on aqueducts in southern Italy. The RAF at that time did not have any suitable aircraft to transport troops over such a long-distance, however, the range of the Whitleys, and their ventral (side) gun turret, which was easily adapted into a jumping position for troops, made it ideal for the task. No. 12 (Blind Approach Training) Flight (later to become No. 1512 (Beam Approach Training) Flight) was formed at Dishforth in September 1941, flying Airspeed Oxfords. In April 1941, No. 78 Sqn was posted to RAF Middleton St George, leaving No. 51 Sqn as the only occupant. In the almost three-year tour that 51 Sqn performed at Dishforth, they flew 1,806 sorties, and lost 50 aircraft (an attrition rate of 2.8%). In early 1942, the Whitleys of 51 Sqn took part in raid on a radar installation in Bruneval, and in Operation Chariot, the raid on St. Nazaire. In June 1942, the first of the Royal Canadian Air Force squadrons, No. 425 (Alouette), was formed with Vickers Wellington aircraft. The squadron set about training and carried out their first raid on the night of the 5 and 6 October. In the same month as No. 425 were undertaking their first operational missions, No. 426 (Thunderbird) Squadron was formed up at Dishforth, becoming operational in January 1943. In January 1943, Dishforth, along with ten other RAF airfields, was handed over from the RAF to the Royal Canadian Air Force (No. 4 Group RAF to No. 6 Group RCAF. Operations were concentrated at Leeming, Linton-on-Ouse and Middleton St George, with substations and the training bases being Topcliffe, Wombleton, Dalton and Dishforth, which had No. 1664 Heavy Conversion Unit. Both Canadian squadrons moved out of Dishforth in 1943;