On October 9, 1st Cavalry Division crossed the 38th Parallel in force and began driving north. ROK divisions had begun crossing the 38th on September 30 and all ROK divisions except the 1st ROK were into North Korea before the 1st American patrols had done so. October 11 7th Cav crossed the Yesong River, and thus all three regiments of 1st Cav were on the assault and NK defenders of Kumchon were trapped in a pocket.

By October 14 Kumchon had fallen, with hundreds of NK KIA and prisoners. These NK troops were mostly in their first combat, but fought well and with determination. They were soundly beaten, but one cut-off group set up a roadblock ambush of a column of artillery and engineers which in retrospect was an omen of the future. The NK killed dozens of US and ROK troops and destroyed or damaged most of their vehicles. As so often occurred in the coming months of battle when the CCF entered, the troops caught in the roadblock appparently made little effort to defend themselves.

For now, however, this was a victory. 1st Cav consolidated its positions and moved on towards Pyongyang.