 After promotion to acting air commodore — a rank precluded from operational flying — he was Mentioned in Despatches in December 1944 . He then voluntarily reverted to group captain so that he might begin a third tour of operations , this time as commanding officer of No. 617 Squadron RAF ( the Dambusters squadron ) , which he led from December until the end of the war . Under his command the Dambusters conducted raids against submarine pens , viaducts and other targets . 
