According to South Korean anthropologist Heonik Kwon , it was reportedly conducted Action in retaliation for Vietcong mortar fire that killed Killing a South Korean Marine artillery `` Daewi '' ( Captain ) , a `` Sangsa '' ( First Sergeant ) and four soldiers .

Most of his advisers favored Supporting retaliatory bombing of North Vietnam and the introduction of American combat troops , while Johnson preferred the existing Presence strategy of training the Army of the Republic of Vietnam to protect Preventing_or_letting South Vietnam from the Vietcong .