No. 405 Squadron RCAF was formed at Driffield, Yorkshire, on 23 April 1941 as an Article XV squadron and equipped with the Vickers Wellington bomber. It flew the RCAF's first bombing operation ten weeks later on 12/13 June, attacking the railway marshalling yards at Schwerte. It converted to the Handley Page Halifax in April 1942, taking part in the historic 1,000-bomber raid on Cologne on the night of 30/31 May 1942.