Populous and rice-rich, the valley was viewed as one of the keys to controlling South Vietnam's five northern provinces by the North Vietnamese and by early 1967 at least two regiments of the PAVN 2nd Division had been infiltrated into the area.

Operation Union II was launched on 26 May to destroy the withdrawing remnants of the PAVN with a helicopter assault by the 5th Marine Regiment, commanded by Colonel Kenneth J. Houghton.

The plan called for 1/5 Marines, commanded by Lieutenant Colonel Hilgartner, to establish blocking positions in the western portion of the valley while the 3/5 Marines, commanded by Lieutenant Colonel Esslinger, was to make a heliborne assault into the southern part of the valley and sweep northeast.

[2]: 68 Supported by artillery and air strikes, Company I enveloped the PAVN's flank, and the Marines soon gained the upper hand.

At 19:00, in total darkness, Companies E, 2/5 Marines and D, 1/7 Marines were inserted by helicopter northeast of the fortified enemy positions and quickly moved south to engage the PAVN's left flank positions in order to relieve battle pressure on the 5th Marine, that were now pinned down by a large entrenched PAVN force The 2 companies quickly moved forward but were soon hit with heavy automatic weapons fire and heavy barrages of large 82 mm high explosive mortar rounds.

When the helicopter returned to Da Nang Air Base, it was noted that it had received a total of 57 holes in its sides from the exploding mortar rounds and automatic weapons fire during the battlefield landing.

The sudden presence of the strong Division Reactionary Force on its northern flank caused the PAVN units to disengage and make a hasty withdrawal to the southwest, but the move proved costly to them.

The following morning, when the battalions swept the battle area, 476 PAVN dead were counted in and around the contested rice paddy and its formidable hedgerow complex and 31 weapons were captured.

[4] This article incorporates public domain material from websites or documents of the United States Marine Corps.