The U.S. Navy spent the 1970s defending a destroyer that many in Congress considered a waste of money. The Spruance class was enormous for a destroyer, yet it went to sea carrying little more firepower than a frigate, and lawmakers said so loudly. Within a decade, those same ships were launching Tomahawk cruise missiles, and the hull beneath them had become the basis for the Navy’s Aegis cruisers. Then, with years of service remaining, the Navy …