Nixon had promised to end the Vietnam War, but at the same time did not want to lose a war. What came of this was the Nixon Doctrine – Vietnamization:
This week, in 1969, at the apex of the Vietnam War, United States President Richard M. Nixon publicly unveiled what would subsequently become known as the Nixon Doctrine. On July 25, during a press conference while visiting Guam, the President announced that the U.S. had plans to increase the training of South Vietnamese troops and bring the American soldiers home. The term “Vietnamization” was the phrase that came to embody that program.
President Nixon's doctrine consisted of three major tenets. First, the U.S. would honor all of its treaty agreements. Secondly, the U.S. would provide a shield if a nuclear power threatened an ally or a country the U.S. deemed to be vital to its national security. And, lastly, the U.S. would provide military and economic aid to countries under treaty agreements, but the requesting nation would be expected to bear primary responsibility to provide the manpower for its own defense. Nixon applied this doctrine directly to Vietnam.The U.S. Army would train the Vietnamese to fight their own war in their own country. The Army of the Republic of Vietnam (ARVN) had already been training with U.S. troops and was organized and supplied with surplus U.S. arms and uniforms. But efforts to build South Vietnamese security forces went beyond just the ARVN. Americans had been working with other indigenous security organizations, as well. One U.S. unit that specialized in training civilian defense groups was the 5th Special Forces Group (Airborne). This unit had been in Vietnam since September 1962 with the primary mission of creating and training civilian security forces. The 5th Group worked with the Civilian Irregular Defense Group (CIDG), the National Police Field Forces and the People’s Self-Defense Force. These groups, composed mostly of local villagers, were trained to help patrol and defend the borders of Vietnam. They originally received eight weeks of training. After the Nixon Doctrine was announced, this period was increased, and many units were eventually redesignated as Ranger Companies or Battalions. Some of the units were attached to the ARVN; others were banded together to form Regional and Provincial Forces. The CIDG transfer to the ARVN or Regional and Provincial Forces was completed by 1971, at which time the 5th SFG (A) returned to the U.S.
The Nixon Doctrine and Vietnamization marked the beginning of the end for U.S. involvement in Vietnam. American Soldiers would use the lessons learned in Vietnam when conducting counterinsurgency training in other nations, such as in El Salvador. The Army is continuing this practice by training Iraqi and Afghan forces in order that they may protect themselves and their countries.
You can also read his speech on this policy. Also check out the full length PBS biography.