to a peaceful solution to the problem of reunification. When not in meetings, Nixon toured architectural wonders, including the Forbidden City, the Ming tombs, and the Great Wall. Americans took their first glance into everyday Chinese life through the cameras that accompanied Pat Nixon, who toured the city of Beijing and visited communes, schools, factories, and hospitals. The visit ushered in a new era of US–China relations. Fearing the possibility of a US–China alliance, the Soviet Union yielded to pressure for détente with the United States. This was one component of triangular diplomacy. Vietnam War When Nixon took office, about 300 American soldiers were dying each week in Vietnam, and the war was widely unpopular in the United States, the subject of ongoing violent protests. The Johnson administration had offered to suspend bombing unconditionally in exchange for negotiations, but to no avail. According to Walter Isaacson, Nixon concluded soon after taking office that the Vietnam War could not be won, and he was determined to end it quickly. He sought an arrangement that would permit American forces to withdraw while leaving South Vietnam secure against attack. Nixon approved a secret B-52 carpet bombing campaign of North Vietnamese and Khmer Rouge positions in Cambodia beginning in March 1969 and code-named Operation Menu, without the consent of Cambodian leader Norodom Sihanouk. In mid-1969, Nixon began efforts to negotiate peace with the North Vietnamese, sending a personal letter to their leaders, and peace talks began in Paris. Initial talks did not result in an agreement, and in May 1969 he publicly proposed to withdraw all American troops from South Vietnam provided North Vietnam did so, and suggesting South Vietnam hold internationally supervised elections with Viet Cong participation. In July 1969, Nixon visited South Vietnam, where he met with his U.S. military commanders and President Nguyễn Văn Thiệu. Amid protests at home demanding an immediate pullout, he implemented a strategy of replacing American troops with Vietnamese troops, known as "Vietnamization". He soon instituted phased U.S. troop withdrawals, but also authorized incursions into Laos, in part to interrupt the Ho Chi Minh trail passing through Laos and Cambodia and used to supply North Vietnamese forces. In March 1970, at the explicit request of the Khmer Rouge and negotiated by Pol Pot's then-second-in-command, Nuon Chea, North Vietnamese troops launched an offensive and overran much of Cambodia. Nixon announced the ground invasion of Cambodia on April 30,