In Operation Birmingham, more than 5,000 U.S. troops, backed by huge numbers of helicopters and armored vehicles, swept through the area around north of Saigon.

Operation Birmingham was a move by the U.S. 1st Infantry Division into War Zone C, which uncovered great quantities of supplies.

In June and July the U.S. 1st Infantry Division and the Vietnamese 5th Division conducted a series of operations, EL PASO II, on the eastern flank of War Zone C in order to open Route 13 from Saigon to the major rubber plantations to the north, as well as to attack the Viet Cong 9th Division massing near the province capital of An Loc. Viet Cong losses were heavy.

The 9th Division withdrew after that action into sanctuaries along the Cambodian border in War Zone C. (Map 3) In late October 1966 this same division deployed its three regiments along with another North Vietnamese Army regiment into central Tay Ninh Province for the purpose of attacking the Special Forces camp at Suoi Da with one regiment while ambushing relieving forces with the other regiments.

At the same time the recently arrived U.S. 196th Light Infantry Brigade was operating in the same area in search of rice and other enemy supplies.