In the aftermath of the major Chinese People's Volunteer Army (PVA) victory at the Battle of the Ch'ongch'on River, the United Nations Command (UN) started to contemplate the possibility of evacuation from the Korean Peninsula.

To prevent the PVA forces from overwhelming the defenders, the US Eighth Army now under the command of Lieutenant General Matthew B. Ridgway evacuated Seoul on January 3, 1951.

[16] Although the Eighth Army was ordered to hold Seoul for as long as possible,[17] UN commander General Douglas MacArthur planned a series of withdrawals to the Pusan Perimeter if UN forces were about to be overwhelmed.

[27] The battle was fought over the UN defenses at the 38th Parallel, which stretches horizontally from the Imjin River mouth on the Korean west coast to the town of Chuncheon in central Korea.

[37] After inspecting the front just days before the battle, General J. Lawton Collins, the US Army Chief of Staff, concluded that most of the ROK formations were only fit for outpost duties.

[45] Responding to Peng's concern over the troops' conditions, Mao limited the scope of the Third Phase Campaign to pin down the ROK forces along the 38th Parallel while inflicting as much damage as possible.

[46] The start date of the offensive was set to 31 December in order to take advantage of the night assault under a full moon and the anticipated low alertness of the UN soldiers during the holiday.

[51] By December 15, 1950, the ROK 1st Infantry Division had retreated back to the town of Choksong on the southern bank of the Imjin River, its original defensive position at the start of the Korean War.

[52][54] The South Koreans had also constructed numerous bunkers, barbed wire obstacles and minefields on both banks of the river in order to strengthen defenses and to maintain troop morale.

[56] PVA "thrust" companies, which were composed of specially trained assault and engineer teams, were also organized to lead the attack across the Imjin and Hantan River.

[65] Upon noticing this development, the PVA 39th Corps decided to use ROK 12th Regiment's flanks as the main points of attack in order to achieve maximum surprise.

[76] The cold winter created great difficulties for the ROK defenders, with the heavy snow hindering construction and icy roads limiting food and ammunition supplies.

[76] The Chinese operational order for the Third Phase Campaign called for the 42nd and the 66th Corps to protect the PVA left flank by eliminating the ROK 2nd and 5th Infantry Divisions,[77] while cutting the road between Chuncheon and Seoul.

[102] With the road completely open between the US rearguards and the British units,[103] the PVA 446th Regiment, 149th Division infiltrated UN rear areas and set up an ambush against 1RUR and the Cooper Force of the 8th King's Royal Irish Hussars.

Ridgway intended that the starting hour of the intermediate move provide time for the 3rd Logistical Command to finish evacuating Inchon, ASCOM City and Kimpo Airfield.

The deadline seemed reasonable since the gradual reductions of stocks at the port and airfield areas since early December already had brought items on hand to modest quantities.

While back shipment at Inchon did continue through the favorable afternoon tide on the 4th, Hill's main attention was diverted to rendering the airfield and port facilities useless to PVA/KPA forces.

Supplies destroyed at Kimpo, ASCOM City and Inchon included some 1.6 million gallons of petroleum products, 9,300 tons of engineer materiel and 12 rail cars loaded with ammunition.

Neither were Milburn's forces as they moved to positions centered on Route 1 at the town of Anyang, nor were Coulter's as they extended the intermediate line northeastward to the junction of the Han and Pukhan rivers.

Creating the delay was not only the sheer bulk of the materiel but also about 100,000 desperate refugees from the Seoul area who crowded the Suwon railroad yards and blocked the trains.

At mid-morning Ridgway radioed Milburn to stand fast until the remaining Suwon stocks had been shipped out and he notified Coulter to leave forces to protect the east flank of I Corps' forward position.

To protect the route from attacks by guerrillas known to be located in the Tanyang area 20 miles (32 km) further east, the 5th Cavalry Regiment had begun to patrol the road from Ch’ungju south through a mountain pass at Mun’gyong.

"Reports so far reaching me," he told the two Corps commanders on the 7th, "indicate your forces withdrew to ‘D’ line without evidence of having inflicted any substantial losses on enemy and without material delay.

Attempting once more to get the quality of leadership he considered essential, Ridgway pointed out to Milburn and Coulter that their opponents had only two alternatives: to make a time-consuming, coordinated follow-up, or to conduct a rapid, uncoordinated pursuit.

An ROK 1st Division patrol moving north over Route 17 during the afternoon of the 7th supported this assessment when it briefly engaged a small PVA group in Kumnyangjang-ni, 11 miles (18 km) east of Suwon.

Although UN casualties were moderate,[123][124][nb 6] the Third Battle of Seoul was a significant success for the Chinese military, and the UN forces' morale sunk to its lowest point during the war.

[127][128] With Ridgway leading the Eighth Army, MacArthur started to regain confidence in UN forces' ability to hold Korea, and the UN evacuation plan was abandoned on January 17.

[131] In the opinion of historian Bevin Alexander, the Chinese rejection of a UN ceasefire had damaged the international prestige it had obtained from its earlier military successes, and this later made it difficult for China to either join the UN or to oppose US support for Taiwan.

[116] US Far East Air Forces' "Interdiction Campaign No.4 ", which was launched on December 15, 1950, against PVA/KPA supply lines, also made the PVA unable to sustain any further offensives southward.

[133] Believing that the UN forces were thoroughly demoralized and unable to counterattack, Mao finally permitted the PVA to rest for at least two to three months, while Peng and other Chinese commanders were planning for a decisive battle in the spring of 1951.