This book presents a collection of authoritative accounts of the evolution and application of Royal Naval shipborne radars during World War 2 in the fields of weapon control, weapon direction, action information and fighter direction. Accounts are also presented of the successful pioneering activities at the Admiralty Signal Establishment in the fields of counter-measures against various enemy electronic systems in active operations, and also of high-frequency direction-finding, ashore and afloat, which, in conjunction with radar, contributed substantially to winning the Battle of the Atlantic.