Battle of FSB Mary Ann

The Battle of FSB Mary Ann occurred when Viet Cong (VC) sappers attacked a U.S. firebase located in Quảng Tín Province, South Vietnam early on the morning of 28 March 1971.

Fire Support Base (FSB) Mary Ann was established to interdict movement of North Vietnamese People's Army of Vietnam (PAVN) and VC troops and materiel down the K-7 Corridor and Dak Rose Trail (branches of the Ho Chi Minh trail running from Laos to the coast of South Vietnam). Originally intended to be a temporary base, it evolved into a more permanent location garrisoned by at least one U.S. Army company. The base was manned by 231 American soldiers at the time of the attack.^: 15

The firebase was scheduled to be handed over to the Army of the Republic of Vietnam (ARVN) when the U.S. 1st Battalion, 46th Infantry Regiment moved north to Da Nang. Twenty-one soldiers from the ARVN Battery B, 22nd Field Artillery, along with two 105mm howitzers, were on Mary Ann to support ARVN operations to the south.^: 137

For months leading up to the attack the level of enemy activity in the area had been low and contacts were infrequent. The lack of significant recent engagements, along with preparations to turn the FSB over to ARVN units, had given U.S. soldiers in the area a false sense of security. The sapper attack was successful, and was described as a "rampage of VC who threw satchels at the command bunker, knifed Americans in their sleep and destroyed all communications equipment".^: 357 Army Chief of Staff William Westmoreland investigated the attack, which resulted in repercussions up the 23rd Infantry Division's chain of command, with the probe citing dereliction of duty, lax behavior and failure of officer leadership as the reasons for the attack.^: 357 Charges were brought against six officers, including the 23rd Division commander and assistant division commander.^: 357