Vietnam. American Air Force planes dropped 24 bombs on the Thanh Hoa Bridge, which until then had withstood, because it had never been directly hit, 638 previous bombings: a monument among hundreds of craters to the carelessness of 20th-century bombing. This time, the 750-pound M-117 bombs, electronically guided, hit the bridge directly multiple times. A simple laser sensor and a pair of Texas Instruments transistors transformed old free-fall bombs with a hit rate of zero in 638 into bombs with a hit rate approaching one in one. This, though it came too late for the Vietnam War, would transform American military power in ways that were clear only to a few specialists at the time.
