On the morning of September 1 , with only the shattered remnants of E Company at hand , the US 9th Infantry Regiment , US 2nd Infantry Division had virtually no troops to defend Yongsan . Keiser in this emergency attached the 2nd Engineer Combat Battalion to the regiment . The US 72nd Tank Battalion and the 2nd Division Reconnaissance Company also were assigned positions close to Yongsan . The regimental commander planned to place the engineers on the chain of low hills that arched around Yongsan on the northwest .