When Walker began spying, he worked as a key supervisor in the communications center for the U.S. Atlantic Fleet's submarine force, and he would have had knowledge of top secret technologies, such as the SOSUS underwater surveillance system, which tracks submarine traffic via a network of submerged hydrophones [REF].
Theodore Shackley, the CIA station chief in Saigon, asserted that Walker's espionage may have contributed to diminished B-52 bombing strikes, that the forewarning gleaned from Walker's espionage directly affected the United States' effectiveness in Vietnam.