Gulf of Tonkin
With no formal troops in Vietnam something needed to happen before troops could be sent to Vietnam. This event was the Gulf of Tonkin which supposedly occurred on August 2nd and August 4th however the event on the 4th was completely made up as documents would prove this in 2005 while the event on 2nd is correct in that a single bullet hit the ship after the ship had fired 3 warning shots. This event eventually allowed LBJ to go to congress and for them to give him a blank check to go do anything in Vietnam using any funding necessary which would be called the Tonkin Resolution.
In 1964 LBJ would win the election and would continue Kennedy's adviserpolicy however in 1965 the Viet Cong would attack a US base. With this attack LBJ would order the strategic bombing of military targets and threats to US airplanes. The bombing must also make sure no other country is brought into the war like China and that there was no danger of heavy civilian casualties.