The U.S. deployed large numbers of military personnel to South Vietnam between 1954 and 1973. U.S. military advisors first became involved in Vietnam as early as 1950, when they began to assist French colonial forces. In 1956, these advisors assumed full responsibility for training the Army of the Republic of Vietnam or ARVN. President Kennedy increased America's troop number from 500 to 16,000. Large numbers of American combat troops began to arrive in 1965. The last American troops left the country on April 30, 1975. At various stages the conflict involved clashes between small units patrolling the mountains and jungles, guerrilla attacks in the villages and cities, and finally, large-scale conventional battles. U.S. aircraft also conducted substantial aerial bombing campaigns, targeting both logistical networks and the cities and transportation arteries of North Vietnam. Large quantities of chemical defoliants were also sprayed from the air in an effort to reduce the cover available to enemy combatants. The Vietnam War was finally concluded on 30 April 1975, with the fall of the South Vietnamese capital of Saigon to North Vietnamese forces. The war claimed between 2 and 5.7 million Southeast Asian lives, a large number of whom were civilians.