On 21 October, two 187th Airborne Infantry Regiment (187 ABN) combat teams started southwards in a reconnaissance-in-force to clear the Sukchon–Yongyu highway and rail line and to establish contact with the 27th British Commonwealth Brigade that was leading the Eighth Army advance northwards from Pyongyang.

The 27th British Commonwealth Brigade had departed from Pyongyang at noon on 21 October, headed north on the Sukchon highway, tasked with reaching the Chongchon River.

The 1st Battalion, Argyll and Sutherland Highland Regiment (1 ASHR), leading the brigade advance, pushed up the highway until fired upon by KPA in the hills south of Yongyu.

An officer with extensive operational experience fighting the Japanese in New Guinea during the Second World War, Green took over from Walsh due to the latter's perceived inexperience.

As such, with a strength of nearly 1,000 men, the addition of 3 RAR gave the brigade increased tactical weight as well as expediently allowing the Australians to work within a familiar organisational environment, rather than being attached to a US formation.

[7] On 16 October, the brigade took over from the US 7th Cavalry Regiment as the vanguard of the UNC advance into North Korea, its axis intended to take it through Kaesong, Kumchon County and Hungsu-ri to Sariwon, then through Hwangju to Pyongyang.

Although the North Koreans had suffered heavily in the preceding weeks, they continued to resist strongly, while a lack of accurate maps and the narrowness of the roads made rapid movement difficult for the advancing UNC forces.

[13] Coad had hoped to rest his men at Pyongyang; however, the advance continued north with little respite and the brigade moved through the village of Samgapo.

[14] The previous day, Colonel Frank S. Bowen's US 187th Airborne Regimental Combat Team (187 RCT) had parachuted into drop zones around Sukchon and Sunchon.

[15] The 187th Airborne Infantry Regiment's 1st and 3rd Battalions (1/187 and 3/187 ABN) dropped southeast of Sukchon to seize the town, hold the high ground to the north and block the highway and rail line south of Sukchon, cutting off the main supply route and line of communication that led north from Pyongyang; the 2nd Battalion (2/187 ABN) was dropped near Sunchon, 24 kilometres (15 mi) east of Sukchon to seize the town, block another highway and rail line, and intercept a POW train that US intelligence indicated was moving northwards by night from Pyongyang.

[18][Note 1] After observing the airdrop, General MacArthur flew to Pyongyang where he announced to the press that the airborne operation was a brilliant tactical maneuver that seemed to have been a complete surprise to the North Koreans.

With a strength of 2,500 men, the regiment occupied positions on the high ground astride the road and rail lines east of Yongyu, 12 kilometres (7.5 mi) south of the US drop zone at Sukchon.

[12] The most important action growing out of the 187 RCT airdrop occurred in the 3/187 ABN sector, about 13 kilometres (8.1 mi) south of Sukchon in the vicinity of Op'a-ri and Yongyu.

I Company reached Op'a-ri at 13:00, where it was attacked by an estimated battalion-strength KPA force equipped with heavy mortars and automatic antiaircraft guns.

After a two-and-a-half-hour firefight, I Company, with two rifle platoons overrun by the KPA and 90 men missing, was forced to withdraw west of the rail line to Hill 281.

Following the capture of Pyongyang, the corps commander, Major General Frank W. Milburn, ordered the advance to continue to the MacArthur Line, running approximately 35 kilometres (22 mi) south of the Yalu River.

[26] Under the command of Lieutenant Colonel George Nielson, 1 ASHR pushed up the road until fired upon by KPA forces in the hills to the south of the town, with snipers engaging the column as it turned west out of the river valley around 16:00.

[29] Following two more KPA attacks, the Americans abandoned the roadblock after running out of ammunition and withdrew to 3/187 ABN's main defensive position 3.2 kilometres (2.0 mi) to the north.

[12][33] By dawn, the North Koreans and Americans had fought each other to a standstill after heavy fighting overnight and the previous day; the KPA 239th Regiment was almost exhausted, yet, in danger of being destroyed, it prepared for a final attempt to break out.

[26] At 09:00, the Australian column was stopped by small arms and light mortar fire from a hillside apple orchard about 1.5 kilometres (0.93 mi) north of Yongyu.

[30] The strong KPA force of approximately 1,000 men allowed C Company, 3 RAR and the battalion's tactical headquarters group to pass before engaging them.

Rather than preparing a deliberate attack and potentially allowing the KPA time to organise their defences, Green chose to force his leading company through at once in order to seize the initiative and continue the pursuit.

[11] Preparing for the assault, Lieutenant Colonel Green informed brigade headquarters of his plans and was advised that 3/187 ABN was believed to be about 1,500 metres (1,600 yd) further north; however, as the exact location of the Americans was unclear, the indirect fire available to support the attack would be limited.

[26] With mortars and artillery unavailable, the Australians proceeded to attack regardless, with the tanks carrying C Company turning east towards the KPA positions in the apple orchard.

[25] Unable to move north, the KPA attempted to escape across the open rice fields to the west, through the gap between the 27th British Commonwealth Brigade and 3/187 ABN.

[26] Following three hours of fighting the battle was largely over by midday; however, many of the KPA that had been unable to escape continued to refuse to surrender, hiding or feigning death until individually flushed out.

In a scene Coad later likened to driving snipe, the Australians proceeded to sweep the area, kicking over stacks of straw and shooting the KPA soldiers they found hiding in them as they attempted to flee.

On 24 October, General MacArthur had removed all restrictions on the movement of his forces south of the Yalu River and prepared for the final phase of the UNC advance, defying a directive of the US Joint Chiefs of Staff and risking Chinese intervention on behalf of North Korea.

[51] On the afternoon of 25 October, a platoon from 3 RAR was fired on by two companies of KPA as they crossed the Taeryong River to conduct a reconnaissance of the west bank, and although they were forced to withdraw, the Australians took 10 prisoners with them.

[52] With the war considered all but over, the 27th British Commonwealth Brigade continued to pursue the KPA towards Chongju; however, the advance increasingly encountered strong resistance as they approached the Manchurian border.