Battle of Onjong

40°6′33″N 125°53′47″E / 40.10917°N 125.89639°E / 40.10917; 125.89639 (Onjong-ri)

The Battle of Onjong (Korean: 온정리 전투), also known as the Battle of Wenjing (Chinese: 温井战斗; pinyin: Wēnjǐng zhàndòu), was one of the first engagements between Chinese and South Korean forces during the Korean War. It took place around Onjong in present-day North Korea from 25 to 29 October 1950. As the main focus of the Chinese First Phase Offensive, the People's Volunteer Army (PVA) 40th Corps conducted a series of ambushes against the Republic of Korea Army (ROK) II Corps, effectively destroying the right flank of the United States Eighth Army while stopping the UN advance north toward the Yalu River.

The Korean War began on 25 June 1950 when the North Korean Korean People's Army (KPA) attacked South Korea. The invasion was almost successful in conquering all of South Korea until the UN intervened, sending ground forces into the country under the command of the United States. The UN forces initially experienced early defeats until the Battle of the Pusan Perimeter, where the UN forces reversed the KPA's momentum. By October 1950, the KPA was effectively destroyed by the UN forces after the landing at Inchon, the breakout from the Pusan Perimeter and the UN September 1950 counteroffensive. Despite the strong objections from the People's Republic of China on North Korea's northern border, the US Eighth Army crossed the 38th Parallel and advanced towards the Sino-Korean border at the Yalu River. As part of the offensive to end the war, ROK II Corps, comprising the ROK 6th, 7th and 8th Infantry Divisions, was ordered to attack north towards the Yalu River through the village of Onjong on 23 October 1950.

In response to the UN advances, Chinese Communist Party chairman Mao Zedong, ordered the People's Liberation Army's North East Frontier Force to enter North Korea and engage UN forces under the name People's Volunteer Army (PVA). In order to stabilize the rapidly collapsing Korean front and to push back the advancing UN forces, Mao authorized the First Phase Campaign, a bridgehead-building operation with the aim of destroying the ROK II Corps, the vanguard and the right flank of the US Eighth Army, advancing up along the Taebaek Mountains in the middle of the peninsula. After the Chinese leadership finally settled the issue of armed intervention on October 18, Mao ordered the PVA to enter Korea on 19 October under strict secrecy.

Onjong is a crossroad village located at the lower Ch'ongch'on River Valley, 10 mi (16 km) northeast of Unsan. At the east of Onjong stands the town of Huich'on, the staging area of the ROK II Corps for the offensive. To the north, Onjong is linked to the town of Kojang, which is located at 50 mi (80 km) away from the Yalu River. Because of the hilly terrain at the Sino-Korean Border, Onjong is one of the few access points into the Yalu River area. The terrain also limits troop movements while providing ideal grounds for ambushes.

On 24 October the ROK 6th Infantry Division of II Corps advanced westward from Huich'on, and Onjong was captured on the same day. From Onjong, the ROK 7th Infantry Regiment, 6th Infantry Division turned north and advanced towards Kojang, while the ROK 2nd Infantry Regiment, 6th Infantry Division planned to advance northwest from Onjong towards Pukchin. Because the UN Command expected no opposition from the destroyed KPA, the advances were not coordinated between the UN units. As a result, the ROK 7th Infantry Regiment managed to wander into enemy territory without much opposition, completely oblivious to the new threats surrounding them.

While the ROK were advancing towards the Yalu River, the PVA were also trying to deploy their units for the upcoming First Phase Campaign. As the PVA Commander Peng Dehuai scrambled to set up his new command post at Taeyudong, the planned advance by the ROK 2nd Infantry Regiment threatened to overrun his position. Without any KPA units nearby to hide the presence of the PVA, Peng was forced to start the First Phase Campaign early by moving the PVA 40th Corps to intercept the ROK 2nd Infantry Regiment near Onjong. On the night of 24 October the PVA 118th Division of 40th Corps arrived at its designated blocking position. Meanwhile, the PVA had set up numerous ambush positions on the ridges overlooking the Onjong-Pukchin road.

On the morning of 25 October and with its 3rd Battalion on point, the ROK 2nd Infantry Regiment started to advance northwest towards Pukchin. The ROK soon came under fire 8 mi (13 km) to the west of Onjong. The 3rd Battalion dismounted from their vehicles to disperse what they thought would be a small force of KPA, but the two PVA regiments on the high ground immediately began pouring heavy fire onto the ROK left, front and right flanks. The 3rd Battalion broke instantly, abandoning most of its vehicles and artillery along the way. About 400 survivors managed to escape the trap and fall back into Onjong.