A leading writer on military intelligence and project director at the Center for Second World War Studies at the University of Edinburgh, Stafford (Churchill and Secret Service) details the political backdrop and events surrounding Operation Stopwatch/Gold—the CIA's clandestine spy tunnel under the Russian sector of Cold War Berlin during the mid-1950s, when Eisenhower complained bitterly about the lack of intelligence regarding Soviet intentions. Although Stopwatch/Gold was the subject of Ian McEwan's 1990 novel The Innocent, adapted into John Schlesinger's 1993 film with Campbell Scott as a telephone technician tapping secret Soviet phone lines, Stafford says his is "the first full-length study of the Berlin tunnel," documenting covert operations and intrigue as complex and dramatic as espionage fiction. Because the British Secret Intelligence Service possessed vital expertise not found in the CIA, the Berlin tunnel became a joint operation, code-named "Gold" by the CIA and "Stopwatch" by the SIS. Originally projected at $500,000, costs soared to $6 million as three large warehouses were constructed to conceal excavations and 3,000 tons of soil were replaced by high-tech eavesdropping equipment. Beginning with the first tap in May 1955, a "vast stream of intelligence" flowed to Washington and London for the next 11 months. In this account of "spies spying on spies," Stafford writes with clarity, and his cool, methodical style adds to the suspense, which peaks in the closing chapters with the April 1956 discovery of the tunnel by the stunned Russians. 29 b&w photos, 3 maps. (Feb.)