Complacency Kills - FSB Mary Ann

In the predawn hours of 28 March 1971, sappers from the VC 409th Sapper Battalion approached the wire of FSB Mary Ann, which was occupied by 231 Soldiers of the 1/46th Infantry, and took up positions to launch an attack. The exact number of sappers involved is uncertain, but most sources agree that there were at least 50. As was common practice for such units, the sappers wore khaki shorts and soot camouflage and were armed with either an AK-47 or RPG-7 and satchel charges and grenades to attack bunkers. Sappers relied on stealth, shock and surprise to give them an advantage, and rarely carried heavy weapons or equipment. The 409th was known to the intelligence section of the 196th LIB, but had previously operated against ARVN targets north of Quang Tin Province. It was assumed by the 196th LIB's intelligence personnel that both the 409th and the 402nd Sapper Battalions were east of FSB Mary Ann, preparing to attack ARVN targets in that region. None of them predicted an attack on the U.S. base.

The ground attack targeted the south side of FSB where the ground gently sloped away from the perimeter. The northeast side was marked by a steep slope toward a river, not advantageous terrain for a sapper attack. The sappers moved in small squads of three to six men, cutting four paths through the base's two outer concertina barriers. They took more time moving through the third barrier, which was about 20 meters from the bunker line, and then fanned out along the southwest side of the line. Following standard sapper doctrine, any attack would begin as soon as the mortar barrage commenced.  The first 82mm mortar shells hit FSB Mary Ann at 02:30, signaling the start of the ground attack.

Once through the wire, the sappers scattered toward key targets: the FSB's artillery, the bunker serving as Battalion Tactical Operations Center (B-TOC), the company command post, and many of the perimeter bunkers. Their attack was aided by tear gas, delivered either by sappers (using grenades) or mixed in with regular high-explosive mortar rounds as part of the bombardment.  Nolan also documents the VC use of CS gas in his narrative of the attack.

The attack against the B-TOC was made easier by Lt. Col. Doyle's failure to post armed guards at the bunker's entrances (which was a violation of brigade policy), preventing any early warning. The sappers used a combination of CS gas and satchel charges in their attack on the bunker (coming at about 02:44 - the time is known because a radio operator in the bunker reported it to the FDC as direct mortar hits and the time was logged), effectively disrupting the command structure on the firebase. At about the same time, the radio operator requested illumination rounds from supporting artillery batteries, but did not indicate that Mary Ann was under ground attack. The south end of the B-TOC was burning by this time, the fire started by a satchel charge igniting a case of white phosphorus grenades located near the south bunker entrance.

The sappers moved through the base from south to north, attacking bunkers and firing positions with grenades and satchel charges. The ground attack lasted about half an hour according to one source.  Once the ground attack was confirmed at 02:50, Doyle requested artillery fire around the hill, a flareship, and gunships. He also asked for medevacs. Artillery at nearby firebases began firing illumination rounds and counter-mortar patterns quickly, but there was "considerable delay" in firing the defensive target (DT) patterns around FSB Mary Ann.  One battery had failed to plot any DTs near Mary Ann, based on the battalion's planned relocation to LZ Mildred, while the artillery officer at FSB Pleasantville delayed firing because the situation at Mary Ann was still unclear. The sappers, of course, prevented Mary Ann's own guns from firing DTs with the speed and surprise of their attack. Cannon crews were defending their positions instead of manning the guns.

Unlike many of the conex bunkers, the B-TOC was of wooden construction and "weatherproofed with tar, so it burned rapidly." After calling for fire support, Doyle made the decision around 02:51 to evacuate the burning structure, and ordered the command staff to relocate to the aid station. Prior to shifting the radios, Captain Paul Spilberg called for artillery fire "fifty meters out, three-hundred-and-sixty degrees around our position." Once the radios had been established at the aid station, he and Col Doyle discovered that Charlie Company's CP (the designated alternate location for the battalion command post) had been hit and partly destroyed.

The Charlie Company CP had been one of the sappers' first targets, and was hit by the first two to three mortar shells of the attack. Constructed mostly of wooden ammunition crates and sandbags, it proved just as vulnerable to fire as the B-TOC. Coming under direct fire from both AK-47s and RPGs, the bunker quickly collapsed. Captain Knight, Charlie Company's commanding officer, was killed in the first few minutes of the attack as were most of his command staff.

Along the base perimeter, most of the troops took cover in their conex bunkers when the mortar barrage began. This allowed the sappers to close rapidly without any danger of return fire, and in many cases they were through the lines before the defenders moved from their bunkers to the sandbagged trench line. The first man to report seeing the sappers had been sleeping on top of his bunker, but didn't spot them until they were "two-thirds of the way to the trench that connected the bunkers."[Many of 1/46th Infantry's casualties occurred during this period and were concentrated among those units along the gently sloping side of the base. Charlie Company's First Platoon, occupying Bunkers 15-19 along the side of the perimeter that had a steep slope, was relatively untouched by the initial assault and manned their positions in the trench line. By contrast, Second Platoon in the southern sector had ten men killed and eleven wounded before Col Doyle and Capt Spilberg moved toward the Charlie Company CP.

Charlie Company's Third Platoon, holding the sector of the perimeter marked by Bunkers 9–13, also took heavy losses. The platoon leader, 1LT Barry McGee, was killed fighting hand-to-hand with sappers, and the teams coming through that sector moved on to attack both the 155mm howitzer position on the high ground to the northwest and the supply elements near the main resupply helipad. The sappers destroyed a number of structures near the pad, killing or wounding a number of Headquarters personnel in the process.

After the initial shock of the attack, some men began to mount effective resistance to the sappers. Shortly after Col Doyle and Capt Spilberg reached the partly destroyed Charlie Company CP, the base's quad .50 began firing, "walking bursts down the hill and into the valley - and straight across into the next hillside". The crew continued firing until dawn, when the four barrels on the weapon burned out. Spilberg also began collecting survivors near the CP and aid station, moving casualties and setting up makeshift defenses.

Although artillery had been firing in defense of Mary Ann since soon after the first word of the attack reached brigade headquarters, it was 03:25 before the first air assets appeared overhead. A Night Hawk helicopter from D Troop, 1st Squadron, 1st Cavalry Regiment (accompanied by a chase ship intended to drop flares and rescue the Night Hawk crew if there were problems) came on station and began engaging targets on the southeast slope of the hill. Forced to break station to refuel, the pilot (Captain Norman Hayes) learned that the additional gunships and medevac helicopters he'd requested when he came on station above Mary Ann had yet to be launched from the airstrip at Chu Lai. Communications failures left both brigade and division headquarters believing that Mary Ann was only being shelled by mortars, making the need for air support appear less critical. While Hayes was refueling, only his chase ship was airborne over the base. They provided what fire support they could using door guns and grenades, and before breaking station to refuel they landed at the VIP pad and picked up "six or seven" of the most critical casualties and evacuated them to Chu Lai.

The sappers had broken contact by the time the brigade commander, Col Hathaway, had his command helicopter land at Mary Ann. Wounded men were being evacuated steadily by this time, and helicopter gunships were making firing runs on targets outside the base's wire. Hathaway's reaction to what he saw on the ground was later described by Capt Spilberg as if "[he] had just walked into Auschwitz."

Hathaway was just the first of a number of higher-ranking officers to fly into Mary Ann. The division commander, Maj. Gen. James Baldwin, arrived shortly after 07:00 to assess the damage. By 09:00 the battalion executive officer arrived to take over from Lt Col Doyle, and at 11:00 Company D was lifted in to replace Company C as the FSB's garrison element. The North Vietnamese took the base under fire with a 12.7mm machine gun at about 16:00 that afternoon, wounding one American and reminding Mary Ann's garrison that they were still under observation.

The battle at FSB Mary Ann inflicted serious losses on the defenders, who suffered 33 killed and 83 wounded. Overall VC casualties remain uncertain, but 15 bodies were located in the aftermath of the attack. Blood trails and drag marks indicated that the VC may have suffered more casualties, but the extent of those losses was never verified.