A pair of North Korean vehicles (T-34/85, SU-76) in Seoul, probably knocked out during the initial North Korean nighttime counterattack on the 1st Marines when the Marines first entered the city.
Operations in Korea—United Nations Offensive. The Department of History, United States Military Academy at West Point.
Mobility and Counter-Mobility
Although counter-mobility was central to the NKPA’s strategy in Seoul, and the 1st Marine Division described “a most skillful delaying action,” the Marines proved capable of pressing the advance. Even before US forces entered the city, the North Koreans had recovered from their initial surprise at the Inchon landings, relying on mines to slow the American advance. The 1st Marines and their supporting armor encountered large minefields along the Inchon-Seoul highway, which damaged or destroyed several vehicles. However, these minefields were sometimes not well camouflaged or covered by fire.
That changed inside the city, where the NKPA combined mines with barricades, and kept both nearby and under the observation of infantry, crew-served weapons, artillery, and tanks. The barricades were mainly composed of earth-filled rice bags, spanned the full width of the street, were approximately ten feet high and five feet thick, and emplaced at every major intersection (200–400 yards). Covering forces were usually waiting in adjacent buildings or on nearby rooftops. Any approach by US forces sparked heavy fire from small arms and crew-served weapons. While the main roads in Seoul were wide, paved, and straight, the secondary roads were not. The North Korean focus on the major roads was prudent as many of the secondary roads were also dead ends. Some of the US troops tried exploring the secondary roads and found them too narrow for their vehicles. Even on the main roads, debris and downed power and telephone lines made travel difficult, causing many flat tires.
These mutually reinforcing elements at each defensive position required US forces to carefully combine many elements of their own capabilities to continue the advance. The infantry-armor-engineer team had to work well together to keep US losses low and maintain the pace of advance. Tanks would move forward and suppress the NKPA fire in the area, so that the engineers could advance and clear the mines. Aircraft contributed by strafing and rocketing. Mines were especially difficult to deal with inside the city because they were harder to find in the rubble and debris in the streets. The infantry would cover the armor, so NKPA infantry could not exploit the limited visibility of the buttoned-up tank crews and charge forward with satchel charges. Once the mines were cleared, the armor would blast holes in the barricades and charge through (some with dozer blades), while continuing to engage enemy forces behind the barricade. Some of the infantry would continue to cover the tanks; others would then clear the nearby buildings and rooftops. US troops repeated this process over and over, the average barricade taking forty-five minutes to clear. Sometimes it took longer, and sometimes tanks were knocked out by mines, but progress was steady. Despite the advantages afforded a defender in urban terrain, and the NKPA focus on counter-mobility, the Marine advance across the city still sometimes exceeded 2000 yards in a day.
While Marine Corps doctrine on urban warfare did not specifically prescribe these methods to clear barricades, they were in line with the spirit of the doctrine. The Marine Corps’ manual on urban warfare mentioned the utility of “obstacles” for defensive urban warfare and the section on street fighting in the Marine Corps’ manual for rifle squads was immediately followed by a section on attacking fortified areas, which it defined as any area where military construction had enhanced the defensive characteristics of the terrain.
The weak link in this choreography of arms was de-mining. While the 1st Marine Division had distributed extra engineer units across the assaulting forces, they were still in short supply. Occasionally the advance stalled while the infantry waited for engineers to arrive. The division’s after-action report called for more training of the infantry in de-mining. When armor was not present, as during the day on 25 September for the 1st Marines, the pace of advance was slower and the cost higher. Several times, when dozer blade-equipped Shermans tried pushing through the barricades without the engineers, they were knocked out by mines.
The Korean War was the debut for one radical improvement in US mobility, the helicopter, but this was not a mode of transportation ready for the urban environment. The first generation HO3S-1 helicopters did facilitate the rescue of downed pilots, medical evacuation, and the movement of commanders around the battlefield, but they were vulnerable to small arms fire. The Marines had only eight helicopters (the only helicopters then in Korea), and several were lost to ground fire, resulting in a command policy to minimize their exposure to fire.
The primary counter-mobility tool for US forces was aircraft. Even several days prior to the Inchon landings, US carrier-borne aircraft were roaming thirty miles inland to attack NKPA forces and restrict any early North Korean reaction. Both US Navy and Marine Corps aircraft maintained a continuous cap of twelve aircraft during daylight hours. On 16 September alone US air units reported destroying 200 trucks just south of the 38th parallel, in addition to seven tanks across the patrol zone. The NKPA response to the danger of daylight movement was to reserve most of its movements for the hours of darkness. To counter this, there were a number of night fighters in use (F7F Tigercats and a night fighter version of the Corsair), some flying from Japan, and then later out of Kimpo. C-47 “flare ships,” each carrying hundreds of one-million-candle-power flares, sometimes supported night interdiction missions.
At night, the two best US counter-mobility tools were mines and harassing artillery fire. Each night US forces dug in, often laying out mines to protect against the frequent NKPA night-time counterattacks. In the large NKPA attack on the night of 25 to 26 September, the lead T-34 was knocked out by a Marine mine. At times harassing fires were directed into Seoul, as the 4.2-inch Mortar Company of the 1st Marines did “throughout the night” of 23 to 24 September.
The firepower-intensive operations in Seoul required large quantities of ammunition, and while strained at times, the American logistical system proved capable of supplying that need. Only two general shortages of artillery ammunition occurred. As the demand for white phosphorous ammunition sometimes exceeded the supply, artillerymen had to substitute high explosive rounds. The Marine 4.5-inch rocket battery was rendered useless because the wrong type of fuses had been brought from Japan, a problem that was not corrected until after Seoul had fallen. This was discovered when a full salvo of 144 rockets was fired into Yongdungpo, supporting the 1st Marines, and not a single rocket detonated. During the NKPA night attack of 25 to 26 September, Marine 105mm howitzer battalions ran low on ammunition, which interrupted their fire missions, before overheated howitzer tubes did the same. Despite those problems, as previously discussed, another US Army artillery unit was in range and was able to shift its support to the Marines in Seoul.
Heavy ammunition consumption by the units in Seoul did draw down the 1st Marine Division’s overall stockpile, but the supply flow was “never seriously interrupted.” This was in part because Marine logisticians aggressively pushed supply dumps forward. By 22 September several were in Yongdungpo, and the first dumps were set up across the Han on 24 September. While American logisticians established no dumps in Seoul until after its capture, one was on the city’s outskirts on the first day of the assault, 25 September.
When local supplies ran low, US personnel usually found a rapid remedy. During that same heavy attack of 25 to 26 September, an emergency request came from the 3rd Infantry Battalion (1st Marines) for more ammunition. The regimental supply dump was moving and could not respond. However, the supply dump for another battalion in the regiment was in place nearby, so several officers using a jeep conducted an emergency resupply from its stocks. They navigated the debris-filled streets at night, directly resupplying the companies in need while under fire. When the regimental dump arrived at 0330 that night, it sent several amphibious trucks full of ammunition to those same companies. Captain Barrow’s Able Company ran low on supplies, as it spent a night isolated in Yongdungpo. His men managed by scavenging some NKPA supplies they captured, and then a resupply run of five American tanks arrived in the morning.
Supplying the tanks in Seoul did present some difficulties, but not sufficiently to detract from their supporting role. Even before the 1st Tank Battalion shipped out from the United States, its personnel discovered a nation-wide spare parts shortage for the M26 Pershing, which logisticians could never solve during the Inchon-Seoul operation. The supply of 90mm high explosive and white phosphorous ammunition for the M26 was low at times (although not “critical”), and tank units shifted to using the Shermans with their 105mm guns. The 1st Marines complained that their supporting armor spent too much time away from the front line refueling and rearming at distant resupply points. At times the advance of the infantry halted until the armor returned. The armor supporting the Marine infantry was a mix of organic and attached from the 1st Tank Battalion, and the Marines found the infantry regiments lacked the maintenance capabilities to support these large contingents of tanks. This was exacerbated by delays in movement of support elements of the 1st Tank Battalion across the Han.
Several operational logistical factors were present during CHROMITE, but the tempo of operations in the city was not affected. Some units experienced resupply difficulties because they had not brought their full complement of trucks, driven by shipping limitations and the rushed planning for the Inchon landings. Another constraining operational factor was the Han. The lack of bridging material, at least before Seoul was cleared, required all units and supplies to move across via motorized pontoon barges, amphibious tractors, or amphibious trucks, creating long lines at the three crossing points. Helping matters was the success of US engineers in rapidly restoring at least partial rail service in the Inchon-Seoul area, and the early capture of Kimpo, into which US transport aircraft flew over 1700 tons of supplies from Japan during the fighting in Seoul (25 to 27 September). US forces also captured significant amounts of NKPA supplies in the advance on Seoul.
Dealing with the Population
During the abbreviated planning phase for Operation CHROMITE, US planners addressed support for the civilian population and stipulated an aggressive schedule for handing over responsibility to the South Korean government. X Corps estimated that 15 percent of Seoul’s population, which had been 1.5 million in 1949, would be destitute and require direct assistance. To that end, the invasion fleet carried with it 2500 tons of rice for distribution to civilians. US intelligence reports on the city included the location of hospitals, water system components, power plants, and lists of those civilians known to be hostile or friendly to the United Nations forces.
Medical care emerged as the salient service provided by US forces to the population. In the first few days after the Inchon landings, only the medical facilities of the 1st Marine Division were ashore, and those facilities were overtaxed supporting the injured from the Marines, Army, Navy, ROK, POWs and “hordes of civilian casualties.” Also in those early days, the 1st Marine Division set up a hospital in Inchon for treating civilian casualties, staffed with US personnel and some “rounded up” local Korean nurses. US forces had some initial difficulty supporting this facility, but this was soon corrected with supplies carried by the assault fleet, flown in from Japan, and captured from the NKPA.
As US forces approached Seoul, it became apparent to the 1st Marine Division Surgeon that the fight for Seoul would generate greater than expected civilian casualties. He took this matter up with headquarters X Corps on 25 September, stating his estimate of five thousand casualties would overwhelm US military medical capabilities ashore at that time, and that there could be political repercussions should this need not be met. Two days later, a letter from the 1st Marine Division commander to Almond estimated a minimum of five thousand civilian casualties and suggested “urgent attention.” Over the next two days, the Marines began establishing two more civilian hospitals, in Yongdungpo and Seoul. Given the overall transport shortfalls for X Corps, few trucks were available to transport civilian wounded, but those most seriously injured were moved in US military vehicles. Out of concern for the spread of insect-borne diseases, resulting from the disruptions to civil services and the number of unburied dead, US forces conducted insecticide “fogging” operations in Seoul and Inchon. Several days before US forces entered Seoul, former city officials were flown up from Pusan on US aircraft, including public health and welfare personnel. Once US forces were inside the city, they established collection points for civilian casualties in the city, and US troops passed captured medical supplies on to the local South Korean officials. In the Inchon-Seoul operation, civilians represented 35 percent of the patients treated by the 1st Marine Division’s 1st Medical Battalion, and the medical company sent by that unit into Seoul actually treated more civilians than it did Marines (615 vs. 518). Additional civilians were cared for at the regimental level, although the 1st Marines’ after-action report identified the need for expanded preparation for this.
Key to the success in the X Corps support of the population was the rapid transition back to South Korean civilian control, something MacArthur had personally emphasized. The Americans flew Seoul’s mayor, police chief, and other city officials up from the south into Kimpo. The mayor of Seoul officially resumed his duties in Seoul’s City Hall on 28 September.
Under direction of the mayor of Seoul a program was initiated to establish the civil police, public health and sanitation, reconstruction of public utilities including water and electricity, and to clear, in general, the destroyed portions of the city.
Civilian police units were slow to reorganize, but US MPs augmented with ROK personnel and self-organized groups of civilians were reasonably effective in restoring order in the city. Marine after-action reports, however, noted that many units needed more civil affairs personnel.
The rules of engagement under which US forces operated in the city allowed for the extensive use of firepower, understandably given the operational military considerations and the nature of the foe. As Puller’s 1st Marines encountered stiff resistance outside of Yongdungpo, he asked for a free hand in applying artillery and air strikes inside the suburb, and Almond “authorized the burning of Yongdungpo.” The 11th Marine Artillery Regiment lamented the lack of proper 4.5-inch rocket fuses as they “Would have been very effective in destroying the town of Yong-Dong-Po.” They also directed extensive harassment, interdiction, and supporting artillery fire into Seoul itself. One Marine 4.2-inch mortar company fired 700 rounds of high-explosive and white phosphorous and reported “the burning out of several blocks within the city.” Restraint in the use of firepower was occasionally evident, but this was most often out of concerns for the safety of friendly military personnel.
An aggressive use of firepower made sense from an operational perspective. The speed at which US forces captured Seoul had a direct connection to the duration of the war in the minds of the American commanders. To that end, US commanders needed an abundance of firepower to overcome the delaying tactics of a determined defender. A shorter war would mean fewer overall civilian casualties. Puller’s mix of regret and determination were evident in his comments to the press.
I am sorry I had to use that stuff [155mm artillery] last night. The Koreans won’t forget this in 500 years. I’m convinced the Reds are holing-up deliberately to force us to use artillery and flame throwers.
Speed was also important for the welfare of the civilians and American POWs. The Marines received reports from informants in the city of NKPA atrocities there, including that approximately 50 percent of the damaged buildings were due to NKPA arson, in a planned scorched earth policy. US units also received reports of American POWs being killed by the NKPA in the city. A captured NKPA memorandum “Directive Re Slaughtering of Captives,” dated 16 August 1950, complained that too many NKPA units were still slaughtering captured Americans, and urged that they should stop as it was no longer useful since the war effort was going so well.
The human cost to the civilian population of Seoul is a moot subject in US after-action reports. The chaos of the battle and the preceding three-month North Korean occupation explain the absence of an accurate count as to the number of civilians actually present in the city, but the number was likely a large proportion of the 1.5 million pre-war figure. Even the official South Korean history of the war avoids the topic. In its eleven-page section describing the battle and handover to South Korean government control, not only is there no estimate of civilian casualties, there is not even a mention of civilian dead. While the duration of the fight inside the city was short, the liberal use of firepower by both sides probably cost considerable civilian life. A gross estimate could be in the low thousands.
The capture of Seoul presented a range of problems, including minimal planning for the fight in the city itself, a hasty operational planning cycle, and some units that were recently created, but US forces overcame these and proved capable of accomplishing their mission. Despite the paucity of attention in the US military to city fighting in the period after World War II, the Marines managed to break through determined resistance at several points outside the city and clear Seoul in just three days. As was the case in Aachen and Manila, the two key drivers behind that success were transferable competence and adaptation.
Carried over from World War II, the USMC’s emphasis on firepower and combined arms—in training, organization, and equipment—paid handsomely on the streets of Seoul. The skillful blending of armor, infantry, artillery, engineers, and air support allowed steady progress against the NKPA barricades—which were themselves a blending of capabilities (mines, infantry, artillery, and armor). When the NKPA chose to attack, Marine firepower was even more effective, as when the NKPA’s offensive capability in the city was largely destroyed on the night of 25 to 26 September. Equally as important, the American logistical system was able to provide the large amounts of ammunition needed for such a firepower-intensive approach. The NKPA did possess some significant armor and anti-armor capabilities, at least on paper, but poor crew quality and training resulted in a decided armor advantage for the Marines.
Unlike the previously examined battles in Aachen and Manila, the Marines at Seoul had no recent experience that carried over into urban warfare. The 5th Marines had just come from the Pusan Perimeter, but none of the American units involved had fought extensively in urban terrain or dealt with the NKPA on the defensive. The quality of Marine personnel, including its small unit leaders, helped make up for that lack of experience. The Marine doctrinal emphasis on aggression and initiative fit perfectly with the needs of the urban landscape. Small unit leaders also contributed greatly to the NKPA’s effectiveness, particularly in the hill mass northwest of the city.
Adaptation by US forces inside the city was minimized by the short duration of the battle, but there were still some examples of adaptation. The 1st Marines’ combined arms solution to the NKPA barricades was not fully applied until their second day in the city, although only because problems with crossing the Han delayed the arrival of its armor into the city. When the US Army first lieutenant could not see the spotting rounds for the badly needed artillery support during the NKPA night attack of 25 to 26 September, he requested a switch to white phosphorous, which proved much more visible amid the many burning buildings.
The greatest difficulties in Operation CHROMITE were induced by higher-level decision making—the relatively low priority given to the isolation of the city, and the direct approach taken by the 5th Marines into the city. Unlike the commanders at Aachen and Manila, Almond gave low priority to cutting off the city before beginning the assault. Perhaps this came from a belief that the city would fall quickly, but his assigning of that task to his two later arriving regiments resulted in the NKPA escape routes remaining open during the battle. A 1st Marine Division intelligence report, produced at the end of the battle, stated,
His [the NKPA] determined delay through the city has afforded him ample time to regroup and reorganize his remaining forces for a determined stand along a line of his choosing.
The route into Seoul from where the 5th Marines crossed the Han took them directly into the NKPA’s main line of resistance. This both delayed the capture of the city and weakened the 5th Marines sufficiently to relegate them to a secondary role in the fighting inside Seoul. Once by plan, and once by accident, US troops entering both Aachen and Manila had managed to bypass the enemy’s main line of resistance.
The battle for Seoul was a decisive point in the Korean War, and probably the most operationally important urban battle in US military history. Of the 70,000 NKPA troops around the Pusan Perimeter, only an estimated 25,000 made it back to North Korea. US forces, mostly Marines, conducted the battle in an aggressive and largely competent manner, ending the first phase of that war. Perhaps most impressively, it was conducted only three months into a war that had shaken the United States out of its demobilized daze. The battle also proved a strong rebuttal to the notion that nuclear weapons had marginalized conventional ground combat operations.