On the morning of 2 January 1963, unaware that their battle plans had been leaked to the enemy, the South Vietnamese Civil Guards spearheaded the attack by marching toward Ap Tan Thoi from the south. However, when they reached the hamlet of Ap Bac, southeast of Ap Tan Thoi, they were immediately pinned down by elements of the VC 261st Battalion. Shortly afterwards, three companies of the 11th Infantry Regiment were committed into battle in northern Ap Tan Thoi, but they too could not overcome the VC soldiers who had entrenched themselves in the area. Just before midday, further reinforcements were flown in from Tan Hiep. The 15 US helicopters ferrying the troops were riddled by VC gunfire and five helicopters were lost as a result.