Every war has its "bridge"—Old North Bridge at Concord, Burnside's Bridge at Antietam, the railway bridge over Burma's River Kwai, the bridge over Germany's Rhine River at Remagen, and the bridges over Korea's Toko Ri. In Vietnam it was the bridge at Thanh Hoa, called Dragon's Jaw.   For many years hundreds of young US airmen flew sortie after sortie against North Vietnam's formidable and strategically important bridge, dodging a heavy concentration of anti-aircraft fire, surface-to-air missiles and enemy fighters. Many American airmen were shot down, killed, or captured and taken to the infamous POW prisons in Hanoi. But after each air attack, when the smoke cleared and the debris settled, the bridge stubbornly remained standing. For the North Vietnamese it became a symbol of their invincibility; for US war planners an obsession; for US airmen a testament to American mettle and valor.   Using after-action reports, official records, and interviews with surviving pilots, as well as previously untapped Vietnamese sources, chronicles American efforts to destroy the bridge, strike by bloody strike, putting readers into the cockpits, under fire. The story of the Dragon's Jaw is a story rich in bravery, audacity, sometimes luck and sometimes tragedy. The "bridge" story of Vietnam is an epic tale of war against a determined foe.