The advance to Mahang-ri and the FBHL had carried the 1st Marines 3,000 yards from its starting point at Ascom City. As the attack continued late in the afternoon, the next objective was Corps Phase Line CC, whose boundaries were defined in the previous chapter. Midway between Mahang-ri and the phase line was the town of Sosa, and it was from this locale that North Korean soldiers were pouring westward to delay the Marine advance on the highway. Since the 5th Marines had veered to the northeast to attack Kimpo, its boundary with the 1st had moved well to the left of the highway. Henceforth, Puller’s regiment would have to go it alone on the main road. This was the case as the 2d and 3d Battalions butted against enemy delaying forces between Ascom City and Mahang-ri, and the isolation became more pronounced as they attacked toward Sosa late on the 17th. Sutter’s unit advanced on the left of the highway with Companies E and F in assault. George Company of 3/1, transported in LVTs and followed by the rest of the battalion, moved along the road behind the 2d Platoon, Baker Company Tanks. There is a defile halfway between Mahang-ri and Sosa, and at this spot the North Koreans chose to make a determined stand. Second Lieutenant Bryan J. Cummings nosed his lead M-26 into the pass, while infantry moved to the shoulders on either side against light opposition. Suddenly the troops and lone tank were hit from the front by a heavy volume of small-arms, antitank, and mortar fire.[267] [267] 2/1 _SAR_; 3/1 _SAR_; and Cummings interv, 24 Aug 54. The Marine infantry was thrown back by the intensity of the outburst, the most severe they had yet encountered. As luck would have it, the engine of Cummings’ tank went dead at this inopportune moment, and the big vehicle stalled. Remembering that infantry had been riding on top of his M-26, the platoon leader opened the hatch to make a quick check. He yanked a lone rifleman inside and buttoned up just as Red soldiers scrambled down the embankment. Fumes from the 90mm gun choked the Marines in the vehicle as they listened to the clamor of North Koreans on the hull. The infantryman who had been pulled to safety by Cummings suddenly went berserk and had to be knocked out. Then the officer was forced to choose between two evils: either his crew must succumb to the acrid fumes or take its chances on opening the pistol port for ventilation. He opened the port. A grenade bounced inside, and the ear-shattering explosion within the steel enclosure wounded Cummings, the rifleman, and one of the tank gunners. At this moment the semi-conscious Marines resigned themselves to the worst.[268] [268] Cummings interv, 24 Aug 54.