On 8 May Nixon authorized the launching of Operation Pocket Money, the aerial mining of Haiphong and other North Vietnamese ports. Nixon had taken a gamble that the Soviet Union, with which he was conducting negotiations for a strategic arms limitation treaty (SALT I), would withhold a negative reaction in return for improved relations with the West. He was correct. The People's Republic of China also muted any overt response to the escalatory measures for the same reason. Emboldened, Nixon decided to launch Operation "Linebacker" a systematic aerial assault on North Vietnam's transportation, storage, and air defense systems on 10 May. During "Linebacker", the U.S. Air Force, Navy, and Marine Corps lost 104 aircraft in combat while their North Vietnamese opponents lost 63.