MACV intelligence, on the other hand was convinced that the incursion would be only lightly opposed. Tactical air strikes and artillery preparations would neutralize the estimated 170 to 200 anti-aircraft artillery weapons believed to be in the area, and the threat posed by PAVN armored units was considered minimal. North Vietnamese reinforcement capability was set at 14 days by two divisions north of the DMZ and it was hoped that diversionary operations would occupy them for the duration of the operation. Unfortunately, when North Vietnamese reinforcements did arrive, they did not come from the north as expected, but from Base Area 611 and the A Shau Valley to the south, where eight regiments, all supported by organic artillery units, were within two weeks marching range.