The 187th Airborne Brigade Combat Team is also taken from X Corps and used as reserve in Seoul. On the west side, 1st Cavalry Division's objectives are a line beginning west of Chorwon down to the Imjin River. The 3rd ID attacks toward Chorwon, the western base of the Iron Triangle. The 25th ID's objective is Kumhwa, the east base of the triangle. The operation kicks off in heavy rain.
Low clouds prevent air support.
Chinese forces, which had been rapidly pulling back into North Korea, put up a strong fight to protect the Iron Triangle. The rain, which turns roads into quagmires, helps the Chinese until June 5. Then, with air cover, ground forces begin to push the enemy back. June 5 - IX Corps' three divisions attack. The ROK 2nd Division and the 7th ID objective is to take the Wyoming line running southeast from Kumhwa to the Hwachon Reservoir.