expected their logistical difficulties in the mountains to slow if not stop their advance within a matter of days; they would have created only a "long bag" that could be closed behind them by rapid drives to block their main routes of resupply and withdrawal. Van Fleet's plan called for I Corps, IX Corps and part of the 1st Marine Division at the left of X Corps to advance on 20 May toward the Munsan-Chuncheon segment of Line Topeka. Once the Topeka segment was occupied, strikes to start closing the bag were to be made toward the Iron Triangle, one up Route 3 to secure a road center in the Yongp'yong River valley some above Uijongbu, another up Route 17 beyond Chuncheon to seize the complex of road junctions at the west end of the Hwacheon Reservoir. There were several reasons to doubt that the 2nd Division could stand on the Han'gye-Nuron-ni line in the X Corps sector. The line was long, there were gaps, and PVA still occupied some of the important ground. General Almond consequently ordered the 2nd Division to withdraw further and the 1st Marine Division to adjust its neighboring positions in accommodation. In anticipation of penetrations of X Corps' lines, Almond also acquired the 187th Airborne Regimental Combat Team from IX Corps for use as a fire brigade in counterattacks. The passage of PVA 27th Army units through the Habaejae area and, farther north, the movement of 20th Army forces in the same southeasterly direction also raised the possibility that the PVA intended to sweep east along Route 20 behind ROK III Corps, turn the east flank of the X Corps, or both. The PVA 93rd Regiment, 31st Division reinforced this possibility when the regiment announced its arrival in Soksa-ri by driving the platoon of the 3rd Division's reconnaissance company out of town during the night of 19 May and by stopping a battalion of the 7th Infantry that attempted to regain the town on the 20th. The 81st Division, 27th Army also revealed its approach on 20 May by engaging the ROK 23rd Regiment, 3rd Division about north of Soksa-ri. Yet even as the PVA IX Army Group appeared to be bringing up reserves and disposing forces for continuing its drive, there were indications that the offensive was losing impetus. Under a pummeling by B-29s, which dropped a hundred seventy tons of proximity-fused bombs ahead