For a hundred years GCHQ Government Communications Headquarters has been at the forefront of British secret statecraft. Born out of the need to support military operations in the First World War, and fought over ever since, today it is the UK's biggest intelligence, security and cyber agency and a powerful tool of the British state.It has been one of the most open-minded, too- GCHQ has always demanded a diversity of intellectual firepower, finding it in places which strike us as ground-breaking today, and allying it to the efforts of ordinary men and women to achieve extraordinary insights in war, diplomacy and peace. GCHQ shapes British decision-making more than any other intelligence organisation and, along with its partners in the Five Eyes intelligence partnership, has become ever more crucial in an age governed by information technology.Based on unprecedented access to documents in GCHQ's archive, many of them hitherto classified, this is the first book to authoritatively explain the entire history of one of the world's most potent intelligence agencies. Many of the major international episodes of the last century including the retreat from empire, the Cold War and the Falklands become fully explicable only in the light of the secret intelligence record. Written by one of the world's leading experts in intelligence and strategy, Behind the Enigma reveals the fascinating truth behind this most remarkable and enigmatic of organisations.