Shortly after his election as U.S. President in 1968, Richard M. Nixon began the long process of negotiating an end to the conflict in Southeast Asia. At the same time, the number of American forces in SEA was gradually reduced in favor of what came to be known as Vietnamization of that conflict. Under the Nixon Doctrine, the U.S. continued to provide diplomatic, financial, and logistical support to Southeast Asian non-communist governments, but to lessen correspondingly the active roles of its own armed forces in those nations. One of the most pressing U.S. demands was for a full North Vietnamese release of American POWs and an accurate accounting of U.S. servicemen missing or killed in action. Late in 1972, a basic North Vietnamese/American agreement was reached and planning for the repatriation of U.S. POWs initiated. As the major staging base for the American involvement in SEA, Clark Air Base was designated as the initial point to which the POWs could return from Hanoi.