Spying has helped the Soviet Union narrow what was once a “significant lead” by the United States in submarine technology, Navy Secretary John F. Lehman Jr. said in an interview published by U.S. News & World Report. Lehman added that the security of the U.S. ballistic-missile submarines has not been undermined by the spy ring allegedly run by retired Navy warrant officer John A. Walker Jr. “It is important to recognize that what makes our ballistic-missile submarines invulnerable . . . depends more on physics and the depths and breadth of the ocean where they hide” than on pieces of paper, Lehman said.