From 1957 to 1965, the war was mainly a struggle between the South Vietnamese army and Communist-trained South Vietnamese rebels known as the Viet Cong. The U. S. provided military advisors. The first U. S. troops entered Vietnam in March . Until 1969, North Vietnam and the United States did most of the fighting. By 1969, the Vietnam War seemed endless, and the United States slowly began to withdraw troops.

The first U.S. troops entered Vietnam in March 1965.

Explanation:

The Vietnam War was a military conflict between North Vietnam on the one hand and the US and South Vietnam on the other, which took place in the territories of present-day Vietnam, Laos and Cambodia. The conflict began on November 1, 1955 after the first Indochina war and lasted until April 30, 1975, when Saigon fell. The war came as a result of the political and military situation during the Cold War, in which communist North Vietnam sought to annex the capitalist South Vietnam, which was under the political and military influence of the United States.  

The first clashes began towards the end of the 1950s and became increasingly common in the early 1960s, so the US sent miltary advisers to South Vietnam. The numbers then tripled each year until the US sent a combat unit to South Vietnam in 1965. Fighting with the North Vietnamese Army and the Vietnamese then spread from the border areas to the interior of the country until they reached the peak of the Tet Offensive in 1968. In 1973, a truce was signed in Paris, after which the Americans withdrew from Vietnam. However, peace did not last long; after a year of relative slack, the war resumed where it ended, except that this time South Vietnam no longer had US aid. The last act of the Vietnam War was the fall of Saigon in April 1975, bringing the conflict to an end after twenty years. More than 1.4 million military personnel were killed in the war, about 6% of whom were members of the United States Armed Forces. Estimates of civilian casualties range from 2 million to 5.1 million.  

the chinese communist party (ccp);

explanation:

the monroe doctrine is the best known u.s. policy toward the western hemisphere. buried in a routine annual message delivered to congress by president james monroe in december 1823, the doctrine warns european nations that the united states would not tolerate further colonization or puppet monarchs.