The Paris Peace Accords, signed on 27 January 1973, specified that a ceasefire would begin at 08:00 the following morning. Both sides understood what that meant: whatever territory you held at the moment the guns stopped was likely what you kept. The South Vietnamese Joint General Staff wanted the south bank of the Cam Lo / Cua Viet River back. Since the Easter Offensive of 1972, North Vietnamese forces had pushed deep into Quang Tri Province. A South Vietnamese counteroffensive in late October 1972 had stalled at the Thach Han River, still five kilometers short of the river line. With the ceasefire deadline approaching, Saigon ordered one more push: recapture the Cua Viet naval base before the clock ran out.

The operation fell to Task Force Tango, a combined force of South Vietnamese Marines and armored units. They jumped off at 06:55 on 26 January, advancing in two columns toward the base. The fighting was immediate and costly. An OV-10 Bronco forward air controller, call sign Nail 89, was hit by an SA-7 missile while coordinating support for a downed F-4 crew. Both crewmen ejected. Radio contact confirmed one was alive and about to be captured. Neither Captain Mark Allan Peterson nor Captain George William Morris Jr. was ever returned. Both are listed as presumptive findings of death. Task Force Tango pressed forward through two days of heavy resistance. At 01:45 on 28 January, the Marines launched a final assault. By 07:00 they had broken through the North Vietnamese lines and recaptured the base, just one hour before the ceasefire.

The ceasefire's arrival at 08:00 on 28 January did not bring peace to Cua Viet. It brought isolation. American support ceased entirely, as mandated by the accords. The Marines had taken the base, but they now held it without naval gunfire, without air cover, without the logistical lifeline that had sustained South Vietnamese operations throughout the war. The North Vietnamese, who had no intention of accepting the loss, waited one day. On the evening of 29 January, they launched a counterattack against the encircled task force. By the following day, they had cut Task Force Tango's lines of communication and begun bombarding the trapped Marines from multiple directions. A Republic of Vietnam Navy landing craft attempting to resupply the Marines was destroyed.

In the early morning hours of 31 January, the Marines attempted to break out of the encirclement. The effort failed to hold the position. North Vietnamese forces recaptured the base, and Task Force Tango fell back with heavy losses: 40 Marines killed and 20 armored vehicles destroyed in the fighting between 28 and 31 January alone. The battle laid bare the brutal logic of the ceasefire. The Paris Peace Accords were supposed to freeze the conflict in place, but the agreement created a final, desperate scramble for territory in which soldiers on both sides died for ground that diplomatic language had already consigned to ambiguity. The men who fought and died at Cua Viet in those last days did so in a strange twilight, where war and peace overlapped and neither side fully honored the line between them.

The Cua Viet River mouth, where the Thach Han River meets the South China Sea in northeast Quang Tri Province, has returned to the rhythms of fishing and coastal life. The naval base is gone. The landscape offers little visible evidence of the desperate fighting that consumed it in January 1973. But the battle remains significant as the last major engagement before the ceasefire, a final spasm of violence at the ragged edge of a war that was supposed to be ending. For the families of Peterson, Morris, and the Marines who never returned, the ceasefire brought no resolution. The battle of Cua Viet belongs to that grim category of military engagements fought not to win a war, but to improve a negotiating position measured in meters of riverbank.