On 20 May, with the objective of reaching the main bodies of PVA/KPA forces, including reserves, before they could organize for defensive action, I Corps commander Lieutenant general Frank W. Milburn set his three divisions on courses for Line Topeka some 15 miles above his Seoul defenses, aiming the Republic of Korea Army (ROK) 1st Division toward Munsan, the US 1st Cavalry Division north through Uijongbu and up Route 33, and the US 25th Infantry Division north along Route 3 toward the road hub in the Yongp'yong River valley.