On September 24, the 1st RCT crossed the river, assaulting directly from Yongdungpo into the heart of the city. With three battalions abreast, the 1st RCT attacked directly east through a series of roadblock barricades that the North Koreans had constructed on the major thoroughfares through the city. The 5th RCT wheeled left, and advanced on the left flank of the 1st RCT as both Marine units systematically cleared barricades, buildings, culverts, and sewers. Both regiments used their M-26 Pershing tanks extensively. Typically a single tank led a Marine infantry platoon as it systematically cleared the interiors of the buildings. The Marine tanks were virtually unstoppable, and easily brushed aside North Korean infantry, and also made short work of a few Soviet-built T-34/85 tanks found in the city.
On September 25, two additional regiments entered the battle for Seoul. One was the 32nd Infantry Regiment of the US Army’s 7th Infantry Division. The other was the 1st ROK Infantry Regiment, attached to the 7th Infantry Division. These two regiments, using the same LVTs as the 1st and 5th RCTs, crossed the Han River into the southern part of Seoul. Thus by September 25, the four allied regiments were on line advancing across Seoul. On the night of September 25–26, the North Korean army mounted a last major counterattack against the 5th, 1st, and 32nd Regiments. The attack against the 1st Marines was led by T-34 tanks and self-propelled assault guns. In the morning the two Marine regiments counted almost 500 enemy dead as well as nine destroyed armored vehicles and eight antitank guns in front of their positions. The steady advance of the three major regiments, supported by the 17th ROK Army Regiment, continued on September 26, and on September 27 the major portion of the city was cleared of communist forces and the X Corps lead elements were pursuing the enemy north through the mountains toward the 38th parallel. It had required 12 days for the X Corps to achieve its objective after landing at Inchon.
The only other major combat formation involved in the battle for Seoul was the 7th Marine Regiment of the 1st Marine Division. This regiment was still en route to Korea when the initial Inchon landings occurred. It landed at Inchon on September 21. The 7th Marines’ role in the Seoul operation was to isolate the city and prevent North Korean forces from escaping the city to the northeast. As the 5th Marines attacked into the city from the north the 7th Marines passed behind them and attacked east. Unfortunately, the direction of attack to the east was across numerous valleys divided by very rugged mountains aligned north to south, and the area was virtually unsupported by roads. Thus, though not strongly opposed, the attack proceeded very slowly. It was only on September 28 that the northeast escape routes were closed, and by then some of the best North Korean troops defending Seoul had escaped.
On September 29, 1950, General Douglas MacArthur and South Korean president, Syngman Rhee, arrived in the capital and General MacArthur declared the city secure. In fact, significant fighting continued as the American units in the city, aided by South Korean forces, continued to systematically clear buildings and streets. Nonetheless, the city was declared secured exactly 90 days after the outbreak of hostilities. The major portion of the 1st Marine Division moved to the eastern portion of the city and prepared to pursue the North Korean army north. Earlier, on September 26, at Suwon, 30 miles south of Seoul, elements of the US Eighth Army linked up with X Corps’ 7th Infantry Division. Between Seoul and Pusan, the North Korean army was completely shattered.
A Fluid Battle
Large urban areas are very difficult objectives to seize except at great cost both in resources and time. The key to the successful capture of a large city, quickly and with minimum expenditure of resources, is to seize it before it is adequately defended. This is extremely difficult to do and can only be accomplished through one of three types of operations: airborne assault; amphibious attack; or a deep rapid armored thrust. General MacArthur recognized that a counteroffensive launched from the Pusan perimeter alone would likely devolve into a long and costly battle of attrition through the Korean mountains, and through numerous large urban areas, including Seoul. The Inchon landing operation, at some significant risk, avoided a war of attrition and resulted in the fall of Seoul in just over 10 days with minimum losses. Unlike most World War II urban battles, the battle for Inchon and Seoul was a battle of maneuver. This was primarily because the attacking force was able to achieve strategic surprise and thus the defender did not have the time to assemble forces and could not establish a comprehensive defense of the entire city area.
The US Marine approach to urban warfare in Seoul was relatively straightforward. Seoul was a huge city which, with Yongdungpo, covered about 80km2 (30 square miles). Despite having more than 20,000 troops available, the North Korean Army had insufficient manpower to defend a continuous line of buildings. The North Korean forces in the city choose to defend fortified barricades oriented on the major avenues and significant natural and city terrain features. The fight for the city became known as the battle of the barricades. Along the city streets the North Korean army erected barricades, constructed of whatever material the North Koreans could find within the city. This included rubble and dirt-packed rice bags, bricks, household furniture, old cars and buses, and any other obstacle-making device they could find. These were torn down by the US and ROK infantry and engineers, or driven over by US tanks. The Marines developed a standard approach to the barricades: artillery fire on the area followed by mortar fire on the position; machine-gun and bazooka fire to suppress the enemy while engineers cleared mines; and finally with the mines removed, the tanks moved forward. The powerful US M-26 tanks were often able to simply plow through the assorted debris. With the tanks came the Marine infantry armed with semiautomatic rifles, fixed bayonets, and grenades. Marine scout-sniper teams overwatched all operations and took a deadly toll on any enemy not behind cover. Each barricade was stoutly defended by North Korean infantry supported by antitank guns, machine guns, and snipers; and took about 45 to 60 minutes to reduce. Thus the movement through the metropolis was of necessity slow, but steady.
A potentially major threat to the US operation was the Soviet-built T-34/85 tanks of the North Korean People’s Army 105th Tank Division. In the march from Inchon to Seoul, 53 of these lethal machines were thrown into counterattacks against the Marines. These tanks had been extremely effective combat vehicles against the best German armor in World War II just five years before. They also furthered their reputation in the first weeks of the North Korean invasion. However, after the initial encounter, the Marines were completely nonplussed by their arrival on the battlefield. They were easily destroyed by a combination of Marine close air support, Marine M-26 tanks, and antitank weapons. By the time the Marines secured the west bank of the Han River, 48 had been knocked out by the Marines and five were found abandoned. In the battle for Seoul itself, the 1st Tank Battalion destroyed 13 T-34 tanks or Soviet-built self-propelled guns and 56 antitank guns, for the loss of five Pershing tanks and two Shermans (most of the American tank losses were to mines and at least one was lost to one of the frequent attacks by North Korean sappers armed with satchels of explosives). Importantly, North Korean armor was of sufficient strength that it could have completely disrupted the US operation, had the US not enjoyed close air and armor support. Thus, armor and close air support were again proven to be very important factors to successful urban combat.
The relatively small size of the US attacking force was possible due to effective air, naval, armor, and artillery support. The air support of the Marines in the Inchon-Seoul operation was particularly effective and noteworthy. Marine aviation units perfected the art of close air support during the Korean War, beginning in the Inchon–Seoul battles. That support was far more responsive and closely coordinated than that achieved by the Marines in World War II. Six Marine squadrons (four day-fighter and two night-fighters) supported the 1st Marine Division and X Corps during the operation. They were controlled by the 1st Division’s 1st Marine Air Wing. They had no other mission other than close air support of the ground forces. Initially the Marines flew in support from two navy escort carriers, the USS Badoeng Strait and the USS Sicily, but once Kimpo airfield was captured, the five F4U Corsair squadrons and the one F7F Tigercat squadron operated from that base, literally minutes from their targets. Close air support was coordinated by Marine Tactical Air Control Squadron 2, which commanded tactical air control parties (TACP) located in each Marine infantry regiment and battalion headquarters. When the US Army 32nd Infantry Regiment entered the battle for Seoul, a Marine TACP was attached to the regiment to give it the benefit of close air support. During the 33-day campaign, September 7–October 9, the Marine aviation units flew almost 3,000 ground-support sorties, including over a thousand in support of the Army’s 7th Division.
Aviation support was critical to the advance from Inchon to Seoul. It was particularly critical to the 5th RCT’s difficult attack south on the east side of the Han River. However, once units entered the city proper the use of close air support became increasingly difficult because of the difficulty of identifying the front line from the air and the danger to the friendly civilian population. Still, even as the battle raged inside Seoul, close air support played an important role aiding the advance of the 7th Marine Regiment through the mountains north of Seoul, isolating the city from reinforcements, and destroying KPA units attempting to retreat from the city.
Politics and Urban Warfare
One of the major characteristics of the fight for Seoul was the intense pressure put on the Marine division to capture the city quickly. This pressure was resented by the Marine officers because speed often caused them to take risks with the lives of their Marines. Often this was viewed as General MacArthur placing politics before the tactical considerations of urban combat. However, there were good reasons to take the city quickly. First, the military advantages of cutting off the bulk of the KPA south of Seoul were obvious. Second, and perhaps most important, were the psychological and political advantages to be gained by recapturing the city less than three months after its capture by the KPA in June. The capital of Seoul defined the allied government of the Republic of Korea and restoring that city to allied control was extremely important strategically to the prestige and legitimacy of the South Korean government. MacArthur understood how strategic Seoul was to the South Korean government, as well as to the UN cause and to the US home front, which desperately needed positive war news. Thus, like many important capital cities in warfare, the strategic value of the city was worth the tactical sacrifices necessary to capture it, and capture it quickly.