Phase III of the offensive began on 17 August and involved attacks in I, II, and III Corps. Significantly, during this series of actions only North Vietnamese forces participated. The main offensive was preceded by attacks on the border towns of Tay Ninh, An Loc, and Loc Ninh, which were initiated in order to draw defensive forces from the cities. A thrust against Da Nang was preempted by the U.S. Marines on 16 August. Continuing their border-clearing operations, three North Vietnamese regiments asserted heavy pressure on the U.S. Special Forces camp at Bu Prang, in Quang Duc Province, five kilometers from the Cambodian border. The fighting lasted for two days before the North Vietnamese broke it off; the combat resulted in the deaths of 776 North Vietnamese, 114 South Vietnamese, and two Americans.
Saigon was struck again during this phase, but the attacks were less sustained and once again easily repulsed. As far as MACV was concerned, the August offensive “was a dismal failure.” In five weeks of fighting and after the loss of 20,000 troops, not a single objective had been attained during this “final and decisive phase.” Yet, as historian Ronald Spector has pointed out “the communist failures were not final or decisive either.” During the same period 700 U.S. troops were killed in action.
The horrendous casualties and suffering endured by communist units during these sustained operations was beginning to tell. The fact that there were no apparent military gains made that could possibly justify all the blood and effort just exacerbated the situation. During the first half of 1969, more than 20,000 communist troops rallied to allied forces, a threefold increase over the 1968 figure. On 5 April 1969, COSVN issued Directive 55 to all of its subordinate units: “Never again and under no circumstances are we going to risk our entire military force for just such an offensive. On the contrary, we should endeavor to preserve our military potential for future campaigns.”