by 4 april, arvn officers had patched together a defensive line that held the pavn at bay, but it was only a temporary respite. although the conventional attack by the north vietnamese, which included the extensive use of armor and heavy artillery, riveted the attention of the allies on the northern provinces, it was only the first of three such operations that were launched that spring. on 5 april, a pavn force of 20,000 crossed the border from their sanctuaries in cambodia in another three-division, combined arms force to attack bình long province, north of saigon. they quickly seized the town of lộc ninh and then surrounded the town of an lộc, cutting the road to the capital. on 12 april, the pavn struck again, this time moving in from eastern laos and seizing a series of border outposts around đắk tô in kon tum province in the central highlands. the pavn then proceeded east toward the provincial seat of kon tum. hanoi had initiated the offensive to coincide with the winter monsoon, when continuous rain and low cloud cover made air support difficult.