by the end of april 1972, the royal lao government (rlg) had lost control of the bolovens plateau and its overwatch of the trail to the invading people's army of vietnam (pavn). a renewed pavn 9th regiment captured the village of laongam and advanced nine kilometers along route 23 into royalist territory. also, during the third week in may, the pavn 39th regiment unexpectedly made a rainy season advance to occupy the town of khong sedone on the banks of the mekong river. this move cut route 13, between savannakhet and pakxe, thus severing the only highway between the two lao military region headquarters. it also essentially divided laos in two, and menaced thai sovereignty.