RAF Coastal Command
During the Second World War, Britain's Royal Air Force was divided into a number of functional and geographic commands in line with an organisation that had first been implemented in 1936. Coastal Command was based in Great Britain and was responsible for all operations over the seas around Great Britain. At the outbreak of hostilities, Coastal Command consisted of three operational groups and one training group, but for most of the war it was organised into five groups. Four of these were operational and responsible for a given a geographic area - 15 Group, north-western Atlantic approaches; 16 Group, English Channel; 18 Group, North Sea; and 19 Group, south-western Atlantic approaches and Bay of Biscay. 17 Group was responsible for training.