No13 Group Fighter Command

During the expansion of the RAF during the late 1930s, the command structure of the air defences of Britain was reviewed. New developments in radar technology and the capabilities of the new Spitfire and Hurricane fighter aircraft, together with the changing nature of the threat posed by the modern bomber aircraft used by the Luftwaffe meant that a comprehensive reorganisation was required. In a command network known as the Dowding System. (an integrated air defence system of radar, raid plotting and radio communication with aircraft)
Fighter Command was divided into four operational Groups, under the control of a central Headquarters at Bentley Priory, North West London. Each Group had its own geographical area of responsibility: 10 Group, South West England and South Wales; 11 Group, South East England; 12 Group, the Midlands; and 13 Group, north of the Humber and all of Scotland. As well as guarding the north during the Battle of Britain, 13 Group also provided reserve squadrons and pilots to the more beleaguered 11 Group which covered south east England. 13 Group also provided quieter bases for squadrons to recuperate from operations.
During the Battle of Britain, the Germans had faulty intelligence indicating that 13 Group had next to no fighters in operation (they believed that the only reason why 11 Group was still holding out was that 13 Group had been sending them down their available aircraft), so they had thought that any attacks made on Scotland would not face any serious resistance. This proved to be a costly mistake for the Luftwaffe, as their bombers were intercepted by a large number of fighters. The bombers could not be escorted all the way to Scotland from Occupied Europe because of the short range of the Messerschmitt 109, plus it was decided to leave out the rear gunner to save fuel so increasing endurance. This was the final nail in the Luftwaffe attack plans and ultimately the bombers proved to be fodder for Air Vice Marshall Saul's Spitfire and Hurricane squadrons.
After the Battle of Britain, 13 Group squadrons helped RAF Coastal Command in patrolling for U-boats and providing air cover for convoys. New pilots would usually find themselves posted to a 13 Group squadron initially so as to gain experience with lesser risk of getting shot down.
After the war, the Group was disbanded on 20 May 1946. However, it was reformed 16 May 1955 before finally disbanded on 31 December 1961 when it was re-designated No. 11 Group.