26 June

Beginning on the afternoon of 25 June, reinforcements started arriving and were committed to battle in succession. The Infantry School Training Battalion was attached to the 11th Regiment, while the Korea Military Academy Training Battalion was assigned to the 13th Regiment, strengthening the main defensive line. The 15th Regiment (consisting of the regimental headquarters and the 3rd Battalion) was attached to the 3rd Battalion of the 20th Regiment and deployed along the Uijeon-ri–Bongilcheon line, which served as the final defensive line. Uijeon-ri is located in present-day Wollong-myeon [ko], Paju, and Bongilcheon is located in present-day Bongilcheon-ri, Jori-eup [ko], Paju.^[6] Colonel Paik Sun-yup, commander of the 1st Infantry Division, centered the division's defenses on Route No. 1, the principal avenue of approach. Anticipating the possibility that the main defensive line might be breached, he planned for the forces stationed along the Uijeon-ri line to cover the withdrawal of the frontline units and launch counterattacks.

On 26 June, North Korean tank units appeared on the front facing Papyeongsan [ko] in Paju, east of the division's sector. The regiment initially engaged the tanks with 2.36-inch M9 Bazooka [ko], but when these proved ineffective, the troops resorted to close-quarters attacks using improvised explosive charges made from Mortar (weapon) shells and Grenade. Faced with these assaults, the tank unit withdrew, and a subsequent attack by North Korean infantry was also repelled in close combat.

Meanwhile, the 6th Division (North Korea) of the Korean People's Army, which had been attacking west of the 1st Division's sector, began an assault before dawn on 26 June, crossing the Imjin River railway bridge with five tanks leading the advance. The Republic of Korea Army's 11th Regiment resisted the attack, but by around 9:00 a.m., a hill north of Munsan Station had fallen to North Korean forces. As this hill overlooked a key route connecting to Route No. 1, the withdrawal routes of the 11th and 13th Regiments were effectively cut off.

However, after capturing the position, the North Korean forces halted their advance and waited for reinforcements. In response, the commander of the 1st Division immediately ordered a counterattack, and at approximately 10:00 a.m. the Korea Military Academy Training Battalion recaptured the hill. Based on information obtained from North Korean prisoners captured during the action, Colonel Paik Sun-yup concluded that only part of the enemy force had crossed the river. Beginning at around 1:00 p.m., he launched a counteroffensive involving three battalions, including the 11th Regiment and the Infantry School Training Battalion attached to it. The counterattack proceeded successfully, and the 1st Division succeeded in retaking its main defensive line.^[7]

However, by this time, Battle of Dongducheon [ko] had already fallen to North Korean forces, and the withdrawal of the 7th Infantry Division (South Korea), which had been defending the city, left the right flank of the 1st Division completely exposed.

The 1st Division (North Korea) of the Korean People's Army advanced toward the Gayeoul(present-day Nogok-ri, Baekhak-myeon [ko], Yeoncheon County)–Jeokseong-myeon, Paju [ko] sector and launched another attack against the Republic of Korea Army's 13th Regiment with tanks spearheading the assault. The 13th Regiment was unable to halt the advance, and as the main force of the North Korean 1st Division pushed westward along Route 320, it began to threaten Munsan.^[8] In addition, North Korean tank units appeared in the rear area of the Republic of Korea Army's 11th Regiment, while attacks from the front also intensified.^[9] Ultimately, Colonel Paik Sun-yup abandoned efforts to hold the main defensive line and, at around 7:00 p.m. on 26 June, ordered a withdrawal to the Uijeon Defensive Line (the Bongilcheon Line), the division's final line of resistance. Under the cover of the 15th Regiment, which had been deployed near Uijeon-ri, the units stationed on the main defensive line successfully withdrew and were redeployed along the Uijeon Defensive Line.^[10]

27 June

Along the Uijeon Defensive Line, the 15th Regiment (including the 3rd Battalion of the 20th Regiment) was deployed at Uijeon-ri along Route No. 1, while the 13th Regiment was positioned at Donae-ri (present-day Wollong-myeon [ko], Paju) along Route 307. The 11th Regiment was held in reserve, forming part of the final defensive line. Meanwhile, the 12th Regiment, which had been forced to disperse and withdraw during the border battles, was being reorganized at Geumcheon (then part of Siheung County).

Beginning at around 10:00 a.m. on 27 June, the main force of the Korean People's Army's 6th Division, spearheaded by tanks, launched an attack against the front of the Republic of Korea Army's 15th Regiment. The regiment had established an anti-tank defense line equipped with 57 mm recoilless rifles and 2.36-inch bazookas, but these weapons proved ineffective against T-34 tanks. As a result, the commander of the 3rd Battalion, 15th Regiment, personally led a suicide assault unit in close-quarters attacks against the tanks, destroying six of them. The Korean People's Army subsequently abandoned the attack and withdrew, while the 15th Regiment succeeded in overcoming its fear of enemy tanks.

During the fighting along the Uijeon Defensive Line, the front held by the 13th Regiment on the right flank of the 1st Division remained relatively quiet. However, from around 7:00 p.m., the regiment's defensive line came close to collapse under a Combined arms by the Korean People's Army's 1st Division. Nevertheless, after successfully destroying two North Korean tanks with 2.36-inch bazookas, the intensity of the enemy assault diminished, and the regiment was able to regain control of its defensive positions.

28 June

During the night of 27 June, taking advantage of heavy rain, North Korean forces launched a night attack that broke through the 1st Division's final defensive line, forcing the regimental units to withdraw from Bongilcheon under cover of darkness. At around the same time, Colonel Paik Sun-yup, commander of the 1st Division, was informed by an operational advisory group led by Major General Kim Hong-il (general), which had been dispatched from Republic of Korea Army Headquarters [ko], of the deteriorating situation along the defensive line in the Mia-ri sector. Anticipating the worst-case scenario, the advisory group recommended that preparations be made for a withdrawal across the Han River (Korea). However, as the existing orders could not be altered, the 1st Division was instructed to hold its current positions for the time being.

At approximately 8:00 a.m. on 28 June, the 1st Division launched a counteroffensive in accordance with its previous orders. The 11th Regiment succeeded in recapturing most of the final defensive line, but the attack by the 13th Regiment on the division's right flank made little progress as it collided head-on with advancing North Korean forces. Colonel Paik Sun-yup committed the Seoul Independent Regiment and the 3rd Battalion of the 20th Regiment to restore the continuity of the defensive line. North Korean resistance on that day was not particularly strong, and the 1st Division assessed that it might even be possible to recapture its main defensive line.^[11]

However, at approximately 1:00 p.m. on 28 June, the Republic of Korea Army's final defensive line at Battle of Miari [ko] was breached by North Korean tanks. Later that afternoon, the 1st Division found its rear areas cut off and lost communications with Army Headquarters. With ammunition supplies also running low, Colonel Paik Sun-yup concluded that it was no longer possible to hold the division's positions and decided to withdraw. The subsequent operations led directly into the Battle of the Gimpo Peninsula [ko] and the Battle of Oryu-dong [ko].

26 June

Chief of Staff Chae Byeong-deok's counteroffensive plan was based on the assumption that the 2nd Infantry Division (South Korea) [ko]would be able to concentrate in the vicinity of Uijeongbu by the morning of 26 June, and that the 3rd Infantry Division (South Korea) and the 5th Infantry Division (South Korea) would also be able to assemble during the course of the day's fighting.^[13] However, Guerrilla warfareactivity in the rear areas severely hampered the movement and concentration of rear-echelon units. As a result, by the morning of 26 June, only the headquarters of the 2nd Infantry Division and two battalions of its 5th Regiment had managed to assemble near Uijeongbu. In addition, although the 7th Infantry Division had a total of five battalions available by the early hours of 26 June, this amounted to little more than the strength of a reinforced regiment.

Under these circumstances, Brigadier General Yu Jae-hung, commander of the 7th Infantry Division, expressed dissatisfaction with the order. Brigadier General Lee Hyung-keun, commander of the 2nd Infantry Division, argued that it would be preferable to wait until the entire division had assembled and its combat power had been concentrated before launching a counteroffensive. He further emphasized the importance of holding the defensive line along the Han River, which offered more favorable defensive terrain.^[14] However, for political reasons, Chief of Staff Chae Byeong-deok ordered that the counteroffensive be carried out. Accordingly, the 2nd Infantry Division launched a counterattack toward the Pocheon sector, while the 7th Infantry Division advanced toward the Dongducheon sector.^[15][16]

Taking into account the fact that recapturing Pocheon with the forces currently available would be difficult, the commander of the Republic of Korea Army's 2nd Infantry Division decided that, after completing its reorganization at Chukseongnyeong [ko] (present-day Soheul-eup [ko], Pocheon) on 25 June, the 3rd Regiment of the 7th Infantry Division would use Chukseongnyeong as a base from which to launch an attack toward Pocheon. As noted above, the only forces available to the 2nd Infantry Division at this time were two battalions of the 5th Regiment. However, the regimental commander of the 5th Regiment was absent, having been assigned to the United States Forces Japan, while the deputy regimental commander was away in Busan. As a result, the regiment was effectively without its senior leadership. Furthermore, when the division departed from Daejeon, it had not received sufficient ammunition supplies. Consequently, it was decided that the regiment would receive logistical support at Chukseongnyeong, and the 5th Regiment began its advance at 3:00 a.m. on 26 June. However, by the time it arrived, the 3rd Regiment, which had been defending Chukseongnyeong, had already abandoned the position and was in the process of withdrawing.^[17] Shortly after reaching Chukseongnyeong, the 5th Regiment encountered North Korean armored units and engaged them with 2.36-inch bazookas and mortars. However, these attacks proved ineffective. Less than ten minutes after the engagement began, the defensive line at Chukseongnyeong—one of the key defensive positions protecting Uijeongbu—was breached by the Korean People's Army.^[18]

Meanwhile, the 7th Division's counterattack initially proceeded successfully. A composite battalion on the right flank of the 1st Regiment succeeded in recapturing Dongducheon. At this point, Lee Kwon-mu, commander of the Korean People's Army's 4th Division (North Korea), began an attack toward the western flanking route through Bongam-ri (present-day Bongam-ri, Eunhyeon-myeon [ko], Yangju) and Deokjeong-ri (present-day Hoecheon-dong [ko], Yangju). The North Korean 4th Division engaged the 3rd Battalion on the left flank of the South Korean 1st Regiment near Hapae-ri (located near Bongam-ri, Eunhyeon-myeon [ko]). However, the 3rd Battalion possessed an effective strength of less than a company, and after approximately thirty minutes of fighting, it was scattered and its position was overrun. The North Korean 4th Division then proceeded to encircle Deokjeong-ri.^[19] At this time, the 18th Regiment, which had been attacking Bongam-ri on the left flank of the Republic of Korea Army's 7th Division, received orders to take up defensive positions in Eunhyeon-myeon [ko], northwest of Deokjeong-ri, after the fall of Chukseongnyeong.^[20] The 18th Regiment engaged a North Korean armored unit in a single battle but was soon overrun. It later defeated a North Korean logistics unit that appeared in front of its position, but thereafter had no further contact with enemy forces, and communications with division headquarters were also cut off. From the early hours of 27 June, the regiment began a phased withdrawal toward Samsong-ri (present-day Samsong-dong [ko], Goyang).

Going further back, on the morning of 26 June, a Republic of Korea Army advisory meeting was held, attended by senior military figures with extensive experience, including Major General Kim Hong-il (general), Chief of Staff of the Army, and Brigadier General Kim Seok-won [ko] (former commander of the 1st Infantry Division). At the beginning of the meeting, Minister of National Defense Shin Sung-mo and Chief of Staff Chae Byeong-deok reported on the progress of the counteroffensive in the Uijeongbu sector and expressed an optimistic view of the situation. However, Major General Kim Hong-il, who regarded the offensive operation in the Uijeongbu sector as overly risky, argued for a decisive battle south of the Han River (Korea), and Brigadier General Kim Seok-won also supported this position. However, the meeting failed to change the policy of the Minister of National Defense and the Chief of Staff, which was to defend Seoul. After the meeting, at an emergency session of the National Assembly, the Minister of National Defense and the Chief of Staff again expressed an optimistic assessment.^[21] However, at around 12:00 noon on that day, the North Korean 3rd Division broke through the defensive line of the Republic of Korea Army's 16th Regiment and continued its advance south toward Uijeongbu. Meanwhile, the North Korean 4th Division, after occupying Deokjeong-ri, was advancing toward Uijeongbu from the northwest while preparing a coordinated offensive.

The Republic of Korea Army's 16th Regiment of the 2nd Division arrived in Uijeongbu slightly later than divisional headquarters and the 5th Regiment, and attempted to block the advancing North Korean forces moving from Chukseongnyeong at Geumo-ri (present-day Jagum-dong [ko], Uijeongbu) northeast of Uijeongbu. The 16th Regiment succeeded in destroying one tank using 2.36-inch bazookas, but, judging the situation to be unwinnable, it withdrew. At Geumo-ri, intense resistance was also carried out by Captain Kim Pung-ik [ko], commander of the 2nd Training Unit of the Artillery School, who personally aimed artillery to halt North Korean tanks, but Uijeongbu was occupied by North Korean forces around 1:00 p.m. on 26 June.

The Chief of Staff reorganized the retreating units at Baekseokcheon [ko] and, holding Brigadier General Lee Hyung-keun, commander of the 2nd Division, responsible for the fall of Uijeongbu, dismissed him. He then appointed Brigadier General Yu Jae-hung, commander of the 7th Division, as commander of the Uijeongbu sector, placing both divisions under unified command and ordering a withdrawal toward Chang-dong.

Following the fall of Uijeongbu, on the evening of 26 June, the Chief of Staff ordered full preparations for the demolition of the Han River bridges. Under the supervision of Chief of Army Engineers Choi Chang-sik [ko], the installation of explosives on five bridges over the Han River^[22]

27 June

At around 1:00 a.m. on 27 June, an emergency State Council meeting convened at the Government-General Building [ko](Central Government Complex) decided to relocate the capital to Suwon. No evacuation plan for the civilians of Seoul had been prepared from the outset, and no mention of such measures was made during the emergency State Council meeting. Subsequently, at a late-night session of the National Assembly, a resolution was passed stating that “Members of the National Assembly will defend the capital to the end together with the one million citizens of Seoul.”^[23] From 5:00 a.m., at a convened high-level defense meeting, Chief of Staff Chae Byeong-deok stated his resolve that “even if the government moves south, the military will hold Seoul.” However, immediately after the meeting concluded, he received a pessimistic report from the front lines stating that “it would be difficult to hold out through the night.”^[24]

At around 3:00 a.m., President Syngman Rhee decided to flee Seoul following persuasion from those around him. At 6:00 a.m., with the government's announcement of the relocation of the capital to Suwon, the citizens of Seoul—who had until then been receiving only optimistic reports—became aware of the seriousness of the capital’s situation for the first time. Civilians seeking evacuation routes crowded onto the Han River bridges and Seoul Station, while reinforcement vehicles continued moving north, plunging Seoul into chaos.

Meanwhile, in Chang-dong, under the cover of the 25th Regiment, which had been partially detached, efforts were underway to reorganize retreating troops withdrawing from Uijeongbu and to establish a defensive line. The 25th Regiment fiercely resisted, destroying three North Korean tanks, and as a result of intense fighting, remnants of the 1st, 3rd, and 9th Regiments of the 7th Division, the 5th, 16th, and 25th Regiments of the 2nd Division, and the 22nd Regiment of the 3rd Division were reorganized into a force equivalent to six battalions. However, the corridor between Dobongsan and Suraksan was highly favorable terrain for mechanized units, placing the South Korean forces at a disadvantage.

Around 10:00 a.m., before defensive positions were fully completed, the Korean defensive forces came under attack by North Korean forces reinforced with approximately 40 tanks and self-propelled artillery. Although the defenders mounted strong resistance with fire support from 105 mm howitzers of the 2nd Training Unit of the Artillery School, they were unable to stop the tanks and the defensive line was breached. Colonel Ham Jun-ho [ko], commander of the 1st Regiment, was also killed by North Korean gunfire, and the ROK forces fell back in confusion, splitting their withdrawal toward the Battle of Miari [ko] and Taereung [ko] sectors.

The withdrawal of ROK forces from Seoul began around 12:30 p.m., and Army Headquarters relocated to Siheung County. However, upon receiving news of possible United States intervention, the Chief of Staff reversed his decision, and Army Headquarters was relocated again to Yongsan District around 6:00 p.m.

Amid this confusion in military leadership, on the Mia-dong–Hwigi-dong [ko] defensive line, Major General Lee Eung-joon [ko], commander of the 5th Division and concurrently commander of the Mia-ri sector, organized a defensive position and reorganized retreating units under his command, including the 2nd Battalion of the 15th Regiment, the 1st Battalion of the 20th Regiment, and the 2nd Battalion of the 8th Regiment of the Capital Division. The Mia-ri defensive line assigned the 5th Division responsibility for the western sector including Route 3, while the 7th Division held the eastern sector. North Korean forces that had occupied Chang-dong temporarily halted their advance, resulting in a lull on the Mia-ri front, while in the Taereung sector, elements of the 9th Regiment and a student volunteer battalion continued to engage in a standoff. At around the afternoon of 27 June, the Mia-ri–Hwigye-dong defensive line was held by a mixed force of approximately 3,000 troops drawn from two divisions. Despite news of possible U.S. intervention and the importance of defending the capital as the final defensive line protecting Seoul, troop morale remained high. The defensive line was located along a sector with a single main access road, which made it favorable for defense,^[25] as blocking the road would effectively halt tank movement. In addition, through the efforts of engineering units and civilians, various defensive works had been constructed around the Mia-ri area, including trenchs [ko], foxholes, and roadblocks.^[26]

On the night of 27 June, North Korean forces launched an attack amid heavy rain. At around 7:00 p.m., a reconnaissance cavalry unit and 10 tanks of the Korean People's Army initiated the first assault. An attempt to halt the advance using explosives laid by engineer units failed, but the attack was repelled once through concentrated fire from heavy weapons, including three 105 mm howitzers.

However, at around midnight the same day, several tanks supported by infantry launched a surprise attack, taking advantage of the rain and shifting the situation. With visibility severely reduced, the Republic of Korea Army defensive units became scattered, and the North Korean armored forces advanced through obstacles. At around 1:00 a.m. on 28 June, a tank unit detached from the 105th Tank Brigade, supporting the 4th Division, crossed Mia-ri, breaching Seoul’s final defensive line.^[27]

The 2nd Battalion of the 8th Regiment, which had been positioned in Hwigye-dong, withdrew due to a shortage of ammunition, while units in the Taereung area continued to engage North Korean forces until the morning of 28 June before beginning a gradual withdrawal. Units on the Mia-ri defensive line continued to hold their positions without being aware that North Korean tanks had already entered the city. However, from the early hours of the morning, they came under attack by North Korean infantry units and began to withdraw.^[28]