On the evening of 30 May 1942, over 1,000 bombers took off for Cologne as part of a dramatic new strategy by Arthur Harris, the recently appointed head of Bomber Command.

That year, Bomber Command typically had around 400 aircraft on a given day, so Harris called in favours. Coastal Command agreed to help and Flying Training Command also lent planes.

At the eleventh hour, Coastal Command withdrew its cooperation as part of the ongoing turf war between the Admiralty and the Royal Air Force, but 'Bomber' Harris was able to scrape together the necessary planes from Bomber Command’s instructional units and trainee crews.