From Wikipedia

Vietnam War: The Real Story

Escalation of the Vietnam War officially started on the morning of 31 January 1965, when orders were cut and issued to mobilize the 18th Tactical Fighter Wing from Okinawa to Da Nang Air Force Base (AFB). A red alert alarm to scramble was sounded at Kadena AFB at 3:00 a.m. F-105s, pilots, and support were deployed from Okinawa and landed in Vietnam that afternoon to join up with other smaller units who had already arrived weeks earlier. Preparations were under way for the first step of Operation Flaming Dart. The mission of Operation Flaming Dart, to cross the Seventeenth Parallel into North Vietnam, had already been planned and was in place before the NLF attack on Pleiku airbase on 6 February. On 7 February, forty-nine F-105 Thunderchiefs flew out of Danang AFB to targets located in North Vietnam. From this day forward the war was no longer confined to South Vietnam. It took almost an hour to get all forty nine of the F-105's in the air. On that morning, the continuous loud roar of the F-105 engines going down the runway, one following another, was described by the ground crew as a "rolling thunder".

After several attacks upon them, it was decided that U.S. Air Force bases needed more protection. The South Vietnamese military seemed incapable of providing security. On 8 March 1965, 3,500 United States Marines were dispatched to South Vietnam. This marked the beginning of the American ground war. U.S. public opinion overwhelmingly supported the deployment. Public opinion, however, was based on the premise that Vietnam was part of a global struggle against communism. In a statement similar to that made to the French almost two decades earlier, Ho Chi Minh warned that if the Americans "want to make war for twenty years then we shall make war for twenty years. If they want to make peace, we shall make peace and invite them to afternoon tea." As former First Deputy Foreign Minister Tran Quang Co has noted, the primary goal of the war was to reunify Vietnam and secure its independence. The policy of the Democratic Republic of Vietnam (DRV) was not to topple other non-communist governments in South East Asia.