An unprecedented publishing event: to mark the centenary of its foundation, the British Security Service, MI5, has for the first time opened its archives to an independent historian. The book reveals the precise role of the Security Service in twentieth-century British history, from its foundation by Captain Kell of the British Army in October 1909, through two world wars, up to and including its present roles in counterespionage and counterterrorism. The book describes how MI5 has been managed, what its relationship has been with government, where it has triumphed, and where it has failed. In all of this no restriction has been placed on the judgments made by the author.

Defend the Realm also adds significantly to our knowledge of many celebrated events and notorious individuals and definitively lays to rest a number of persistent myths. Above all, it shows the place of this previously extremely secretive organization within the United Kingdom. Few books could make such an immediate and extraordinary increase to our understanding of British history over the past century.

The history of espionage is far older than any of today’s intelligence agencies, yet the long history of intelligence operations has been largely forgotten. The codebreakers at Bletchley Park, the most successful World War II intelligence agency, were completely unaware that their predecessors in earlier moments of national crisis had broken the codes of Napoleon during the Napoleonic wars and those of Spain before the Spanish Armada.

Those who do not understand past mistakes are likely to repeat them. Intelligence is a prime example. At the outbreak of World War I, the grasp of intelligence shown by US President Woodrow Wilson and British Prime Minister Herbert Asquith was not in the same class as that of George Washington during the Revolutionary War and leading eighteenth-century British statesmen.

In this book, distinguished historian Christopher Andrew recovers much of the lost intelligence history of the past three millennia–and shows its relevance today.

Based on unprecedented access to a secret archive of intelligence, The Sword and the Shield presents by far the most complete picture we have ever had of the KGB and its operations in the United States and Europe, revealing for the first time the full extent of its worldwide network.

Vasili Mitrokhin worked for almost thirty years in the foreign intelligence archives of the KGB. Mitrokhin spent over a decade making notes and transcripts of these highly classified files which, at enormous personal risk, he smuggled daily out of the archives and kept beneath his dacha floor. Now he has offered Christopher Andrew exclusive access to his archive. The picture that emerges in this sobering book will force us to acknowledge that there was indeed an enemy—and that he was very much in our midst.