Recount the stages of Johnson's escalation of the Vietnam War up to 1967. Why did the conflict become a "quagmire"?

At firs Johnson sent advisers and gave weapons to the South Vietnamese so that they fight the North Vietnamese. Later on U. S. bombers bombed parts of North Vietnam and ground troops were committed to assist the South. More and more troops were being sent until the U. S. became deeply involved in the conflict. When public support decreased, the U. S. began its withdrawal from South Vietnam.