The battalion then mounted a disorganized retreat to Cheonan several miles away, having failed to significantly delay the North Korean forces in their movement south.

On the night of June 25, 1950, 10 divisions of the North Korean People's Army launched a full-scale invasion on the nation's neighbor to the south, the Republic of Korea.

The force of 89,000 men moved in six columns, catching the Republic of Korea Army completely by surprise, resulting in a disastrous rout for the South Koreans, who were disorganized, ill-equipped, and unprepared for war.

At the time, the closest forces were the 24th Infantry Division of the Eighth United States Army, which was headquartered in Japan under the command of Major General William F. Dean.

[7] During that time, the 24th Division's 34th Infantry Regiment, with 2,000 men organized into the 1st and 3rd Battalions, was the second US unit into Korea, and was sent by rail north from Pusan.

The 1st Battalion, 34th Infantry emplaced at Pyongtaek, 10 miles (16 km) south of Osan, to block the next North Korean advance.

[8] Pyongtaek was a village consisting mostly of wooden huts and muddy roads[9] In the meantime, 3rd Battalion, 34th Infantry was emplaced at Anseong, several miles east.

The soldiers of the battalion were equipped with only M1 Garand rifles or other weapons, C-rations, and less than 100 rounds of ammunition each, whilst only one M2 Browning machine gun was available to each platoon.

The team attempted to destroy a tank it spotted in the village of Sojong but was unsuccessful; it suffered one killed (Private Kenneth R. Shadrick) and was forced to return to Pyongtaek.

[20] Shortly after, several survivors from Task Force Smith arrived at 1st Battalion's command post telling stories of their defeat at Osan, but Ayres did not believe they were accurate.

[28] Within fifteen minutes, B Company was able to return fire effectively, and by this time the North Korean forces had advanced steadily toward 1st Battalion's position.

A Company, under the heaviest attack, attempted a gradual withdrawal which quickly became disorderly, as men ran from the hill, some without weapons and ammunition, being strafed by North Korean machine guns the entire time.

[26][32] Company commanders gathered what men they could and began moving south, though one-fourth of 1st Battalion was killed, missing or captured immediately after the brief fight.

The retreating elements left a trail of equipment behind, littering the road back to Pyongtaek with ammunition, helmets, and rain gear.

[29][36] The 34th Infantry Regiment began to set up a new line south of Chonan by nightfall, even though many of its men no longer had equipment to fight with.

[37] The engagement at Pyongtaek had caused a significant decline in morale among American forces fighting on the peninsula, and this would continue until victories at Inchon and the Pusan Perimeter allowed them to go on the offensive.

[29] Dean took the blame for the defeat himself, and historians consider him at least partially at fault for expecting one inexperienced battalion to hold the line against a numerically superior enemy who was well-trained.

The 24th Infantry Division would continue to fight in delaying actions such as this one for two more weeks until it was overwhelmed at the Battle of Taejon, however by that time the Pusan Perimeter would be in place, and other US divisions would be able to hold the line for several more months during the Battle of Pusan Perimeter until the Inchon Landings, when American forces would finally defeat the North Korean Army, ending the first phase of the war.