Larry Berman

“Xuan Thuy. The president did not want either his secretary of defense or the Joint Chiefs to know about the meeting. Unbeknownst to Kissinger, Laird decided to make use of the top-secret National Security Agency (NSA) and Defense Intelligence Agency (DIA) to monitor White House back-channel activity. The NSA is the Department of Defense’s communications espionage agency; the DIA is its all-source military intelligence agency. Laird told each of the military men he selected to spy on the White House that “they’d better be loyal to me.” He promised each four stars after four years and kept his promise.27 From this deal, Laird got all the information he needed about Kissinger’s contacts with foreign governments, his secure telephone conversations, and the back-channel messages on his secret conversations in Paris with Le Duc Tho and on the SALT negotiations.28 “Henry was very smart, but Mel was smarter,” observed former secretary of state George Shultz. “Mel enjoyed”
― Larry Berman, Zumwalt: The Life and Times of Admiral Elmo Russell "Bud" Zumwalt, Jr.

“the bureaucratic in-fighting and was a match for Henry.”29 NSA operatives intercepted all back-channel messages, and the U.S. Signal Corps tracked White House conversations. The Special Air Missions branch of the air force controlled the planes that Kissinger used for his secret trips.30 Laird often knew Kissinger’s destination before Henry did, which is probably the reason Laird reportedly had advance knowledge of Kissinger’s secret trip to Beijing. Laird never let Kissinger in on the fact that he had this information.”
― Larry Berman, Zumwalt: The Life and Times of Admiral Elmo Russell "Bud" Zumwalt, Jr.