Question

president johnson escalated american involvement in vietnam by

Answer 1

LBJ reversed Kennedy's order to withdraw 1,000 of the 16,000 troops in South Vietnam. He got authorization from congress to to expand the number of troops and change their role. They had been advisors and trainers.
The Gulf of Tonkin Resolution was based on false reports the the North Vietnamese had attacked the USS Maddox twice.
In that resolution LBJ got a blank check. He could send as many troops as he wanted and do with them whatever he wanted without having to go back to Congress again.
The American forces became combat troops fighting the war for the South Vietnamese instead of supporting the South Vietnamese to fight the war themselves.
LBJ escalated the war every year from 1964 to 1968.
He ended his presidency by not running for re-election in 1968, Virtually admitting defeat. He didn't want the US to be seen as losing a war.
The country elected Richard Nixon on the promise that he would end the war. Nixon did end the war and had Peace Accords signed by the beginning of his second term as president. He and Secretary of State Kissinger were masters at foreign affairs.

We were out of Vietnam and returned to Kennedy and Eisenhower's plan of a support role. But Nixon was paranoid and allowed a cover up of a burglary by his 1972 campaign staff. He was pilloried and forced to resign.
After he was gone, Congress needed to kick him good one last time. They voted to cut all aid and support to South Vietnam. So our allies stood helpless to invasion by the North. All the lives lost unnecessarily under Johnson and the brilliant work for peace under Nixon was lost.

The image of the US Embassy being evacuated in Saigon as it fell to the North is what most people remember. And they blame that on Nixon. It is actually the picture of defeat snatched from the jaws of victory by a Congress who hated a man enough to sacrifice a democracy so the man's legacy would look worse than it was.