By that stage, Vann was frustrated by the Civil Guard soldiers of Task Force B, because they appeared to be in no hurry to reach Ap Bac, as they searched one house at a time while marching up from the southwest flank of the battlefield. In his final effort to defeat the VC, Vann flew into Tan Hiep and asked Cao to deploy an airborne battalion on the east side of Ap Bac, the most logical retreat route for the Viet Cong. Vann hoped to trap the Viet Cong inside the hamlets by blocking their retreat routes on all sides, and annihilate them using an elite battalion of South Vietnamese paratroopers. To Vann's disappointment, Cao strongly opposed the idea and decided to drop one of his airborne battalions behind the M113 formation on the west side instead. Vann accused Cao of wanting to let the VC escape in order to avoid further South Vietnamese casualties. However, Cao argued that a surrounded and well-entrenched enemy would fight more fiercely than a retreating one, so he wanted the VC units inside the hamlets of Ap Bac and Ap Tan Thoi to expose themselves by retreating through the eastern side of the battlefield, where he could destroy them with artillery and air power. Cao had also lost confidence in Vann, because Cao felt Vann had placed the lives of many South Vietnamese soldiers at risk to save the lives of a handful of Americans. Major-General Tran Thien Khiem, Chief of the ARVN Joint General Staff, was present during the argument. He did not object to Cao's plan because it was consistent with President Diem's objective to save Vietnamese lives through the Rural Revolutionary Development and Chieu Hoi Programs, which encouraged VC fighters to join the South Vietnamese military.