Retired Army Col. David Hackworth, a decorated Vietnam veteran who spoke out against the war and later became a journalist and an advocate for military reform, died Wednesday in Mexico, where he was receiving treatment for bladder cancer, his wife said. He was 74. "He died in my arms yesterday morning," his wife, Eilhys England, said Thursday. Hackworth, a syndicated columnist for King Features, advocated a streamlined military and improved conditions for troops.