The Vietnam War spanned the terms of Presidents Eisenhower, Kennedy, Johnson, Nixon and Ford. Each president was tormented by the seemingly unwinnable war unfolding in Indochina, and with the exception of Presidents Nixon and Ford, all were committed to winning the war somehow. However, it was President Nixon who made the decision to instead commit the United States to developing South Vietnamese forces to protect against North Vietnam and other invading nations. Thus, the Nixon Doctrine was not directly focused on containing communism or defending developing nations through declarations of war against aggressors, but was instead focused on developing the native military forces of those nations requesting aid and providing a such nations have the means to protect themselves. from external and internal threats. The Nixon Doctrine was immediately applied to the second half of the Vietnam War after the Nixon administration moved into the White House. The doctrine's primary purpose was to address methods by which the United States would extricate its military forces from Vietnam, while at the same time helping South Vietnam defend itself from China-backed North Vietnam. According to the Encyclopedia of the New American Nation regarding the Nixon Doctrine:Southeast Asia would be the context for the most visible application of the Nixon Doctrine. In an effort to extricate the United States from the Indochina War, Nixon sought to "Vietnamize" the conflict by having indigenous troops supplant American forces. This was a program that took four years to complete, with the last US troops leaving Saigon in 1973. (2011)During the process of extrication from Vietnam, the Nixon administration implemented the Nixon Doctrine...... half of the document... ...itedGholz, E. (2009). World Politics Review. The Nixon Doctrine in the 21st Century. Retrieved July 2, 2011, from EBSCOhostKhmer Rouge. (2011). The History Channel website. Retrieved July 2, 2011, from http://www.history.com/topics/khmer-rougeMeiertöns, H. (2010). US security policy doctrines: An assessment under international law. Cambridge University Press. Retrieved July 2, 2011, from EBSCOhostThe Nixon Doctrine (2011). In The Encyclopedia of the New American Nation. Retrieved July 2, 2011, from http://www.americanforeignrelations.com/AD/Doctrines-The-nixon-doctrine.htmlRavenal, E. C. (1971). The Nixon Doctrine and our commitments in Asia. Foreign Affairs, 49(2), 201-217. Retrieved July 2, 2011, from EBSCOhostRoskin, M., & Berry, N. (2010). IR: The new world of international relations: 2010 edition (8th ed.). San Francisco, CA: Longman/Pearson Education.