David Hackworth, the celebrated soldier and public figure, died yesterday at the age of 74. Hackworth volunteered for military service at 15, won three purple hearts in Korea, and was the youngest colonel in Vietnam, where "he became an almost mythical [combat] figure." In 1996, Charles Krohn and David Plotz wrote about the "the self-regarding, self-parodying military macho man," a correspondent for Newsweek at the time. "When will his employers—who know better, or ought to—stop pretending that his macho posturing and potted strategic sermonettes constitute journalism?" they asked.