Richard Nixon took office in 1969 having promised to extract the United States from Vietnam through what he called an "honorable peace." Ultimately his strategy, heavily influenced by his National Security Adviser Henry Kissinger, became known as "Vietnamization." The plan was to shift the burden of fighting the war against communism in South Vietnam to the South Vietnamese Army. Nixon's order to invade Cambodia in 1970 was part of this strategy--he thought that the Viet Cong was using bases within Cambodia to attack American and South Vietnamese positions in South Vietnam. In other words, he saw it as a defensive measure intended to bring about the stability needed to ultimately withdraw. Many Americans did not see things this way, however--to them the invasion looked like an escalation of the war, the opposite of what Nixon had promised to do. The invasion of Cambodia led to some of the most strident protests of the war, including the tragedy at Kent State. By 1972, the administration was locked in negotiations with the North Vietnamese government, and Nixon's decision to bomb Hanoi was an attempt to strengthen the hand of American negotiators (including Kissinger). The bombing of Hanoi, known as the "Christmas bombing," was one of the largest bombing campaigns in American military history. Whether it achieved its goal is open to debate, but the Paris Peace Accords, which ended US involvement in the region, were signed  a little more than a month later. Still, this bombing campaign, like the invasion of Cambodia, was very unpopular in the United States, with even Republican politicians criticizing the decision as inhumane.