A savvy, revisionist rundown on airwave espionage as practiced mainly by the British, albeit with a sufficiency of information on their friends and foes. West (A Thread of Deceit, M16, etc.) implies that government agencies' attempts to intercept and analyze message traffic began just shortly after Marconi invented the wireless, and he proceeds to track efforts to extract intelligence from radio signals from the turn of the century through the present era--a task in which satellites and high-speed computers now figure strongly. The author recounts the vital role played by sigint in release of the Zimmermann Telegram at the height of WW I; the breaking of Japan's diplomatic code long before Pearl Harbor; Cold War overflights by the U-2 and other high-altitude aircraft; Israel's 1967 assault on the Liberty; North Korea's capture of the Pueblo (another spy ship); the USSR's willingness to pay well for the telecommunications and cryptographic secrets of NATO nations; and widespread violations of civil rights by putatively open regimes. West's centerpiece, though, is a series of debunking disclosures on the Ultra intelligence that accrued from the UK's ""crackling"" of Nazi Germany's Enigma ciphers during WW II. Errors and breaches of security on the part of enemy operators, he shows, ranked among the principal reasons the Allies were able to obtain so much valuable military and diplomatic information. The intellectual prowess of Oxbridge dons employed at Bletchley Park helped them make the most of enemy miscues. But they never did break the German Navy's code, and consistent observance of mandated safeguards probably would have made Enigma transmissions invulnerable. (Gordon Welchman told much the same tale in The Hut Six Story. As the admiring West makes clear, however, government officials on both sides of the Atlantic put an effective lid on this 1982 book and hounded its author to an early grave.) A fine briefing on a covert trade that's the cloak-and-dagger equivalent of a growth industry.