Vietnam War remained in the field for four days. Tellingly, South Vietnamese forces were again defeated in June 1965 at the Battle of Đồng Xoài. On 8 March 1965, 3,500 U.S. Marines were unilaterally dispatched to South Vietnam. This marked the beginning of the American ground war. U.S. public opinion overwhelmingly supported the deployment. The Marines' initial assignment was defensive. The first deployment of 3,500 in March 1965 was increased to nearly 200,000 by December. The U.S. military had long been schooled in offensive warfare. Regardless of political policies, U.S. commanders were institutionally and psychologically unsuited to a defensive mission. General William
Vietnam War artillery, and airstrikes. The U.S. conducted a large-scale strategic bombing campaign against North Vietnam. Following the Tết Offensive, U.S. forces began withdrawal under the Vietnamization phase; the Army of the Republic of Vietnam unconventional and conventional capabilities increased following a period of neglect and became modeled on heavy fire-power focused doctrines like US forces. Operations crossed international borders: bordering areas of Laos and Cambodia were used by North Vietnam as supply routes and were heavily bombed by U.S. forces. Gradual withdrawal of U.S. ground forces began as part of "Vietnamization", which aimed to end American involvement in the war while