The National Committee for a Sane Nuclear Policy (SANE) and American socialist Norman Thomas appeal to North Vietnamese President Ho Chi Minh on behalf of captured American pilots. The number of American captives was on the increase due to the intensification of Operation Rolling Thunder, the U.S. bombing campaign against North Vietnam. On July 15, 18 senators opposed to President Lyndon B. Johnson’s Vietnam policy signed a statement calling on North Vietnam to “refrain from any act of vengeance against American airmen.” The next day, the United Nations Secretary General also urged North Vietnam to exercise restraint in the treatment of American prisoners of war. On July 19, North Vietnamese ambassadors in Beijing and Prague asserted that the captured Americans would go on trial as war criminals. However, Ho Chi Minh subsequently gave assurances of a humanitarian policy toward the prisoners, in response, he said, to the appeal he received from SANE and Norman Thomas. Despite Ho’s assurances, the American POWs were routinely mistreated and tortured. They were released in 1973 as part of the provisions of the Paris Peace Accords that were signed on January 27, 1973.