On December 4th,
the Mobile Riverine Force moved to Sa Dec and 3rd and 4th Battalions, 47th Infantry, with the 5th Marine Battalion, began operations to find and destroy elements of the 267th Main Force and 502nd Local Force Battalions in Western Dinh Tuong and Eastern Kien Phong Provinces. The battle that ensued on December 4th-5th proved to be one of the most severe the Mobile Riverine Force had yet experienced.
Early on December 4th the force encountered major elements of the 502nd Local
Force Battalion in a fortified base on the west bank of the Rach Ruong Canal.
The enemy attacked the boats with rockets and automatic weapons and a decision was made to land the Marine Battalion to the north of the enemy position. Shortly afterward the 3rd Battalion, 47th Infantry, was landed south of the enemy position. Fighting was intense and Colonel David directed the 4th Battalion, 47th Infantry, which was standing by at a pickup zone, to land west of the enemy location. Mid afternoon of December 4th, the Vietnamese Marine Battalion made a frontal assualt that overran the enemy's major bunker complex. Supporting fire from armed helicopters and assualt craft contributed largely to the assualt's success. To the south, the 3rd Battalion, 47th Infantry, encountered stubborn resistance from