It was located near the Vietnamese Demilitarized Zone (DMZ) about 3 kilometers (1.9 mi) from North Vietnam in Gio Linh District, Quảng Trị Province.

[3]: 18  Con Thien was intended to be used as a base for the McNamara Line to prevent People's Army of Vietnam (PAVN) infiltration across the DMZ.

In mid-April Charlie Company, 11th Engineer Battalion was tasked with clearing a 200m wide strip from Con Thien to Gio Linh, a distance of 10.6 km.

By 19 April, despite harassment from PAVN mines, small arms, recoilless rifle, mortar and artillery fire the strip was half-completed.

[3]: 44 At 03:00 on 8 May some 300 rounds of mortar and artillery fire hit the base, while PAVN sappers with Bangalore torpedoes breached the perimeter wire.

[5]: 21 [8] Base commander Captain Chamberlain received the Distinguished Service Cross and purple heart for his valor and leadership in repulsing the attack.

[5]: 23 From 13–16 May, 1/9 Marines cleared Route 561 from Cam Lo to Con Thien fought a well-entrenched PAVN force south of the base.

[5]: 29 For the remainder of Operation Hickory the Marines encountered only scattered resistance but discovered and destroyed numerous bunkers, ordnance and rice.

Companies M and L attacked the complex but were forced back by small arms, machine guns, 57mm recoilless rifle and 82mm mortars for the loss of 2 Marines killed and 21 wounded.

Numerous medevac missions were flown to transport wounded Marines to medical facilities at Dong Ha and to the hospital ship Repose.

[11] Time magazine featured the story on the cover of its 6 October 1967 issue, which was instrumental in bringing the reality of Vietnam combat to American readers.

[12] David Douglas Duncan's photos of the Marines at Con Thien were featured in the 27 October 1967 issue of Life magazine and in his book War Without Heroes.

CBS News broadcast a special report on 1 October 1967, The Ordeal of Con Thien, hosted by Mike Wallace, which featured footage and interviews from the field.

The troops then sandbagged existing bunkers with a "burster layer" in the roofs, usually consisting of airfield matting to burst delayed fuse rounds.

[3]: 127 On 29 January a Marine observer at Con Thien using a Starlight Scope spotted a PAVN convoy moving about 1 km north of the Ben Hai River and called in artillery air strikes.

[3]: 127 By the end of January the defensive positions on the trace line, including C-2, C-2A and Con Thien (A-4), were largely complete, although there was abundant evidence of continued PAVN infiltration across the DMZ.

[3]: 357 On 7 July, to exploit the results of Operation Thor in the Cua Viet-Dong Ha sector, the 9th Marines began a sweep of the area between Con Thien and the DMZ.

[3]: 387 On 15 August, a PAVN company attacked a four-man Marine reconnaissance team southeast of Con Thien near the abandoned airstrip at Nam Dong.

Of special interest were repeated sightings of low, slow moving lights during hours of darkness which, it was assumed, came from enemy helicopters thought to be resupplying forward positions with high priority cargo such as ammunition and medical supplies or conducting medevacs.

On 19 August, after 60 Arclight strikes 2nd Battalion 1st Marines (2/1) assaulted into three LZs in the Trung Son region of the southern DMZ, 5 km north of Con Thien.

Responding with accurate rocket, mortar, and artillery fire, the Marines forced the PAVN to break contact and withdraw to the north.

[3]: 389 On 24 August at 17:00, Marine reconnaissance team Tender Rancho was moving 7 km southeast of Con Thien near Dao Xuyen, when it surprised a group of 15 bivouacked PAVN troops killing 6.

During the remainder of the 25th and into the 26th, as Companies C and D, 1st Marines pushed southward toward the other blocking forces, the PAVN made several unsuccessful attempts to break the cordon.

[3]: 391 On 11 September, Company D, 11th Infantry engaged a PAVN force of unknown strength from the 27th Independent Regiment occupying bunkers near the "Market Place," 4 km northeast of Con Thien.

[3]: 392 On 13 September following Arclight and naval and land artillery strikes 3 Battalion task forces from the 5th Infantry Division attacked into the DMZ northeast of Con Thien.

To the east the ARVN 1st Squadron, 7th Armored Cavalry, supported by two platoons from Company A, 3rd Tank Battalion, simultaneously attacked to the north and northeast of A-2 and Gio Linh.

On the left flank, after encountering mines and antitank fire, the three Army task forces joined the action, claiming to have killed 35 PAVN and seizing a large cache of mortar rounds.

In coordination with the ARVN 2nd and 3rd Battalions, 2nd Regiment, and the 3rd Marines, the companies moved to a position west of Con Thien and then attacked north across the southern boundary of the DMZ, toward the Dong Be Lao mountain complex.

[3]: 394 Despite heavy rain during October, ground and aerial reconnaissance missions indicated the presence of a sizable PAVN force south of the Ben Hai River between Gio Linh and Con Thien.

While ground reconnaissance would be a part of the effort, attended and unattended detection devices or sensors would provide a majority of the surveillance capability.