At 22 : 30 the fog lifted and Kouma saw that a North Korean pontoon bridge was being laid across the river directly in front of his position . Kouma 's four vehicles attacked this structure , and after about a minute of heavy fire the bridge collapsed , and the ponton boats used to hold the bridge in place were sunk . At 23 : 00 a small arms fight flared around the left side of A Company north of the tanks . This gunfire had lasted only two or three minutes when the A Company roadblock squads near the tanks received word by field telephone that the company was withdrawing to the original ridge positions and that they should do likewise .