High Quality Content by WIKIPEDIA articles! The Cambodian Campaign (also known as the Cambodian Incursion) was a series of military operations conducted in eastern Cambodia during mid-1970 by the United States (U.S.) and the Republic of Vietnam (South Vietnam) during the Vietnam War. These invasions were a result of policy of President Richard Nixon whose decision it was to invade. A total of 13 major operations were conducted by the Army of the Republic of Vietnam (ARVN) between 29 April and 22 July and by U.S. forces between 1 May and 30 June.