In the aftermath of the Dunkirk evacuation of the British Expeditionary Force in May 1940, the British started on the development of a substantial raiding force under the umbrella of Combined Operations Headquarters. This was accompanied by the development of techniques and equipment for amphibious warfare. In late 1941, a scheme was put forward for the landing of 12 divisions around Le Havre, assuming a withdrawal of German troops to counter Soviet success in the east. From this came Operation Rutter to test the feasibility of capturing a port by an opposed landing, the investigation of the problems of operating the invasion fleet and testing equipment and techniques of the assault.