American M-26 tanks roll in as the UN forces retake the South Korean capital in the Second Battle of Seoul.
September 25 was the first day of fighting in Seoul itself, mostly by the 1st Marines. On this first day in Seoul, however, Puller’s men had to fight without their armor support. The crossing site used by the 1st Marines on the previous day lacked the heavy pontoon barges needed to move the tanks, so the tanks had to drive further north, to the location where the 5th Marines had first crossed. Those tanks made it across the Han on the morning of the twenty-fifth, but poor terrain, enemy contact, and mines all combined to keep them out of the city for the day. Even without that support, elements of the 1st Marines pushed 2000–2700 yards into the city, against heavy enemy resistance, before setting up their night-time defensive positions.
Delays in the 5th Marines’ efforts to clear the northwest hill mass prompted Almond to order the 32nd Infantry Regiment and 17th ROK Regiment (paired with the 32nd) to attack into the city from the south. On the morning of the twenty-fifth, the 32nd Infantry did just that, crossing the Han in amphibious tractors, advancing toward their objective of South Mountain, or Namsan to the Koreans. After driving 3500 yards north, aided by fog and surprise, they captured their objective by 1900, a 260-meter hill overlooking the city. While South Mountain itself was not urban terrain, it was important for the visibility it gave of the entire city. The 32nd Infantry was quickly followed across the Han by the 17th ROK Regiment, which then turned right to capture a series of hills to the east.
The 5th Marines spent the twenty-fifth with split duty, with some of its troops clearing the rest of the hills at the edge of the city, and others pressing into Seoul. The 7th Marines were north of the city, where they remained throughout the battle. X Corps had assigned them a series of high-ground objectives lying just north of the city.
The North Korean reaction to these initial penetrations into Seoul was twofold. First, they started moving forces out of the city to the northeast, apparently thinking this was an option soon to be precluded by the American advance north and south of Seoul. Second, they launched several strong counterattacks against US units in or at the edge of the built-up area. Unfortunately for X Corps, Almond recognized only the first reaction.
Earlier, on 25 September, US aerial reconnaissance had reported a large number of enemy leaving the city to the northeast. This led Almond to conclude the North Koreans were in full retreat, and he then ordered the 1st Marine Division, late that night, to conduct an immediate attack. The 1st Marine Division commander, Maj. Gen. Oliver P. Smith, objected strenuously, but he was overruled by the X Corps chief of staff, and Smith set 0200 (26 September) for both the 1st and 5th Marines to attack.
Just minutes before the attack was to commence, a forward reconnaissance patrol for the 1st Marines reported that a major enemy counterattack was about to begin in their sector. Puller reacted by calling in all the artillery support he could get, and his men spent the rest of the night in what was arguably the largest urban fire fight in US military history. The Marines estimated the attacking force as at least a full battalion of infantry, supported by heavy mortars and fourteen tanks and self-propelled guns. Puller’s men held, supported by seven tanks, decimating the attackers. It was an indication that the fight for Seoul would be more like that for Yongdungpo than Inchon. Also hit that night were the 5th Marines and the 32nd Infantry Regiment. The attack on the 5th Marines was smaller, but approximately one thousand NKPA troops struck the 32nd Infantry in their positions. One company of the 32nd was overrun before US reserves threw the attackers back by morning.
X Corps had assigned the majority of Seoul to the 1st Marine Division. The 1st Marine Division tasked the 5th Marines with a smaller zone, in the northwest of the city, probably in recognition of the heavy losses they had suffered clearing the hills outside the city. The 1st Marines were assigned the largest sector, a wide strip through the center of the city, starting from the southwest corner and continuing to the northeast edge. X Corps assigned the remainder of the city to the 32nd Infantry Regiment and the 17th ROK Regiment. X Corps attached several battalions of Korean marines to various US units to aid with mopping up and flank protection.
On the morning of 26 September the assault recommenced, and US forces soon learned the rest of the NKPA defensive plan. At most intersections, North Korean forces had set up barricades made mostly of rice bags filled with dirt. These barricades were covered by infantry in nearby buildings, mines in front of the barricades, and often artillery and/or tanks. US troops quickly developed a process for breaking through each barricade, but it was time consuming. The 1st Marines were able to advance 1000–1500 yards to the northeast against heavy resistance that day, while the 5th Marines made “limited gains” against similar resistance in their sector. The 32nd Infantry Regiment, along with the 17th ROK, continued to push eastward, taking more of the high ground between the city and the Han, and inflicting heavy losses on enemy columns moving east of the city.
On 27 September the 32nd Infantry Regiment pushed north and west of South Mountain, to clear parts of the city not in the zone of the 1st Marines, making contact with the Marines before noon. The 5th Marines pressed on in their sector, initially against heavy resistance, but by late afternoon they were mopping up. The 1st Marines continued to advance against a “most skillful delaying action,” while South Korean marines mopped up behind them.
By the afternoon of 28 September, organized resistance in the city was broken, with the remaining NKPA forces having retreated out of the city to high ground to the north and east. The 17th ROK Regiment and the 7th Marines had both advanced eastward, although at no time during the battle was the city cut off. “By late afternoon, both Division Commanders reported Seoul had been cleaned up except for very minor sniper fire.” Mines were still a significant impediment to movement through the last remaining portions of the city, but the battle was over.
Command, Control, and Communications
Several operational factors made command and control in Seoul difficult. The first was the short time available for planning. The plan for the Inchon-Seoul operation, Operation Plan 100B, was not published until 12 August, and the X Corps headquarters was not operational until 31 August. The short planning cycle led to many ad hoc command arrangements and disorganization in units and personnel. The planning rush kept the focus on the big picture, and left many details to be worked out later. A dearth of intelligence on crossing sites for the Han was a key factor.
Since exact river crossing sites could not be predetermined, detailed plans for the seizure of Seoul could not be prepared by division until the lower downstream crossing of the Han had been secured.
After the 5th Marines had crossed the Han, Almond met with the 1st Marine Division and 7th Infantry Division commanders, to plan the assault on Seoul. Smith wanted a frontal assault from the northwest to punch through the increasing resistance facing his 5th Marines, with all three of his infantry regiments, while Almond favored attacking the city from several directions. Almond gave Smith his frontal assault, although with a deadline of 24 September to enter Seoul. When that did not happen, Almond ordered the 32nd Infantry Regiment and the 17th ROK Regiment to cross the Han northward into Seoul on the twenty-fifth.
The other crucial operational factor was Almond himself. Having spent the preceding eighteen months before the landings as MacArthur’s chief of staff, Almond shared some of MacArthur’s over optimism and taste for publicity. When the 5th Marines crossed the Han on 20 September, MacArthur told the commander of the 5th Marines that the NKPA forces would “evaporate very shortly.” On several occasions Almond told Smith that he wanted Seoul captured by the twenty-fifth, so he could issue an announcement on the three-month anniversary of the North Korean attack. When the rate of advance was substantially behind this timeline, Almond declared the city captured anyway, just before midnight on 25 September. Almond was strongly influenced by intelligence reports from X Corps reconnaissance aircraft that large numbers of NKPA troops were leaving the city, just prior to dusk on 25 September.
Based on that information, at 2040 on 25 September, Almond ordered the 1st Marine Division to attack into Seoul immediately. “You will push attack now to the limit of your objective in order to insure maximum destruction of enemy forces.” Smith was aghast, and he called back to X Corps to explain,
The inadvisability of attacking at night in an unfamiliar oriental city the size and complexity of Seoul, and in which there was no indication of the enemy fleeing the Division front.
The X Corps chief of staff told him the order stood. The two large counterattacks that hit just minutes before the Marines were to launch their own attack demonstrated the considerable gap between conditions in Seoul and Almond’s perception. Almond’s diary makes no mention of this episode, with no entries from 1700 on the twenty-fifth until 0900 the next morning. Smith’s reaction may have been a reflection of USMC doctrine at the time. A 1949 USMC manual on urban combat states,
The larger the town and the longer it has been occupied by the enemy, the more thorough must be the preparations for the attack.
The critical difference between Almond and Smith was that the 1st Marine Division commander saw Seoul as a fundamentally more difficult objective. Mirroring his superior’s error at Manila, Almond did not think the enemy could or would fight seriously for the city. Chesty Puller’s vision for Seoul was more accurate, when he predicted to a news correspondent that the North Koreans would defend Seoul in a manner that would require the Marines to destroy it. Fleet Marine Force Pacific commander Lt. Gen. Lemuel C. Shepherd Jr. shared Puller’s outlook, telling MacArthur shortly after the 5th Marines crossed the Han, that the NKPA would fight to the last in Seoul.
Two other significant command errors occurred. Failure to foresee the NKPA main line of resistance resulted in the primary American thrust into the city being delayed for several critical days, during which substantial NKPA forces continued their escape northward. The 5th Marines’ drive into the city, from the northwest, ran headlong into the primary NKPA defensive position. From a topographical standpoint, the hill mass northwest of Seoul should have been viewed as a likely major defensive position, even more so given its history as a training ground for both Japanese and South Korean troops. A 1st Marine Division photo interpretation report, dated the day before the 5th Marines crossed the Han (19 September), referenced the “entire area” north of the Han and Kimpo as having been used by the Japanese and Koreans for training, and also mentioned numerous empty defensive positions. Had this hill mass been bypassed to the north, it is difficult to imagine the NKPA defense being as effective as it was. The NKPA forces in those hills might have moved out and counterattacked the 5th Marines, but the Marines proved themselves most capable at handling such counterattacks throughout the Inchon-Seoul campaign. Almond and Smith share the blame for this error, Almond for being fixated on a particular date of liberation, and Smith for insisting on the most direct, but also the most predictable, route into Seoul from the 5th Marines’ crossing point on the Han.
The other error was the low priority Almond gave to isolating the city. Almond put too much emphasis on capturing the city itself, rather than denying its utility as a transit point to retreating NKPA forces. He focused on the tactical while losing sight of the operational. Almond assigned the task of cutting off the city to the later-arriving 7th Marines and 32nd Infantry Regiment. This resulted in an escape route out of the city to the northeast remaining open during the battle, when resistance slowed the advance of the first two Marine regiments. Given the resources available to Almond, cutting off the city would not have been an easy task, but the low priority he gave that effort increased the likelihood his forces would fail to trap any NKPA in the city.
The two key regimental commanders, Murray of the 5th Marines and Puller of the 1st Marines, were both highly experienced and decorated. In eighteen months of combat operations in the Pacific in World War II Murray had won two Silver Stars and a Navy Cross. Puller, already a legend in the Marine Corps, had won four Navy Crosses by this point in his career. Prior to Seoul, they had never met, although once it became clear the two regiments would be clearing Seoul side-by-side, Murray flew over to Puller’s command post in a helicopter. Helicopters were sometimes used by high ranking officers (e.g., Almond) to visit units forward, but this does not appear to have been the case for units inside the city.
Once inside the city the styles of Murray and Puller differed. Murray used as little artillery as possible, doing minimal artillery preparation and relying on his forward commanders and artillery observers to call in artillery on identified enemy positions. After the battle he was particularly proud, and the South Koreans thankful, that the Korean president’s house (the Blue House) in his sector was not destroyed. While Puller had sometimes been criticized during World War II for not using enough supporting arms, in Seoul he used artillery heavily.
Establishing and maintaining contact between units in the city proved difficult at times for US forces. On the night of the heavy counterattacks (25 to 26 September), the 5th Marines were unable to make contact with the 1st Marines to their south, and the 7th Marines just north of the city could not make contact with the 5th Marines to their south. Over the course of 26 September, the 1st Marines made contact with the 5th Marines on their left and the 32nd Infantry Regiment on South Mountain on their right. The likely cause was the shorter lines of sight in the urban terrain, as compared to the usual open Korean countryside. As the Marines moved into the city, the requirement for troops per unit of distance to maintain visual contact would have changed considerably. Apparently they adapted, although with some modest delay.
The control and integration of Marine aircraft into the combined arms team was outstanding. On-station Marine aircraft could deliver close air support as quickly as artillery, and were “always immediately available” during the day. X Corps attached Marine air controllers to Army units, and this offered such a radically improved level of support over what the Army units were used to from the Air Force that the Marines had to “conduct a running seminar on how to use air support.” In January 1951, the then-commander of the 7th Infantry Division wrote a letter to the commandant of the Marine Corps praising the quality of the close air support given his division by the 1st Marine Air Wing over the previous four months. He cited over one thousand sorties without a single friendly casualty. Marine units were also pleased with the “excellent” quality of their air support, with some targets engaged within one hundred yards of friendly units.
There were no significant command and control problems across service and national boundaries in Seoul. During the heavy NKPA counterattack early on 26 September against the 1st Marines, fire support duties were skillfully handed off from Marine artillery to Army artillery, by lower ranking officers, even though the Army artillery had been previously tasked by X Corps to support another unit. An Army staff sergeant from an Army tank unit attached to a Marine regiment found working with Marine infantry effective. Several battalions of Korean marines were attached to the 5th and 1st Marines, along with some Korean National Police, and they worked well clearing out bypassed pockets of NKPA and stragglers disguised as civilians. Almond attached the 17th ROK Regiment to the 32nd Infantry Regiment, and those two units worked well in clearing out the high ground to the city’s southeast. Almond had given extra attention in the planning of CHROMITE to coordination between the 1st Marine Division and the 7th Infantry Division.
Almond’s rules of engagement for artillery and aircraft were liberal. Unit reports and personal recollections from the battle make few references to restrictions on the use of firepower. The restrictions that are mentioned relate to unit boundaries, suspected prisoner of war holding facilities, and certain historic structures. The mindset was apparent on 20 September, when the 1st Marines reported, in a rather business-like fashion, they were “leveling the southern part of Yongdungpo.” The controls in place were apparently sufficient in terms of limiting losses due to friendly fire as only a few instances occurred.
While there were significant communications problems inside Seoul, they were less so than during the rapid movement phase toward the city. The pace of advance from Inchon was too fast for US communications specialists to lay wire, which then placed a heavy burden on radio equipment. The Marines found their radios too heavy, insufficient in range, disrupted by hilly terrain, fragile, and powered by weak batteries. One exception was the SCR-300 backpack radio, which the 1st Marines called “the best, and most valuable, piece of equipment rated by the infantry regiment.” Once inside the city both the 1st and 5th Marines reported better communications, probably because the slower pace of advance allowed wire-laying activities to catch up. Communications with aircraft were functional but still in need of improvement, both for aircraft and ground units. The age of Marine radios was an issue, many having been in storage since World War II. The Marines did encounter two urban-specific communications problems: signal blockage from steel-reinforced buildings, and frequencies that were close enough to commercial radio frequencies that interference resulted. In one case, a company from the 1st Marines spent a night isolated in the heart of Yongdungpo out of radio contact. The company had found a gap in the NKPA line and its battalion headquarters ordered it to press forward. By sunset, when the company had set up on a key hill inside Yongdungpo, its radio’s batteries had run out, and it is unclear how much was known about this company’s situation by other units. The regimental commander, Puller, stated in an interview years later, that he was unaware of the company’s location until the next day.
That same company’s night alone provides insight into the quality of American small unit leaders. Its commander, Captain Robert H. Barrow, recognized the value of the terrain his company occupied, and he held that hill all night, despite being out of contact, under repeated heavy attack, and low on ammunition. Barrow was not the only example of high quality small unit leadership in the difficult urban environment. While only minutes from executing orders to attack into Seoul itself, more of Puller’s small unit leaders were able to quickly shift into a defensive posture and hold back the powerful NKPA night-time attack of 25–26 September. Marine small unit commanders also proved adept at orchestrating combined arms, with the support and weapons pushed out to smaller units, particularly as was needed for dismantling the NKPA barricades. This level of performance was particularly notable as Puller’s regiment conducted the bulk of the clearing operations inside Seoul. Unlike Murray’s 5th Marines, which had experience inside the Pusan Perimeter, the 1st Marines had been hastily assembled in the United States just prior to the Inchon landings. They had less time to come together as a regiment, placing greater demands on those small unit leaders. The Marine Corps urban manual emphasized this when it stated urban combat “Will resolve itself into small independent actions; and will place a premium upon initiative and aggressiveness of the small unit commander.”
In sum, there were considerable problems with higher level command and control, particularly the decisions made on how to enter and isolate the city. And yet, once fighting in the urban landscape, command and control at the regimental level and below was effective in clearing the city.
Intelligence and Reconnaissance
US intelligence reports prior to the landings included detailed maps of the city down to the individual building level, but the estimates of NKPA troop strength (5000) were almost half of the actual strength (8000–10,000).114 The reports did describe accurately the rear area quality of most of the units, the presence of anti-aircraft and engineer units, and the limited ability of the NKPA to reinforce the Seoul area. Interestingly, American intelligence personnel gave significant attention in their pre-landing intelligence estimates to the possibility of Chinese intervention in the battle for Seoul, as distinct from an approach to the Yalu. “Although the international implications of such a move are considerable, the possibility cannot be overlooked.”
American tracking of the locations and strength of NKPA units during the battle proved challenging, with the arrival of many units into the area, the NKPA’s re-designation of some units, and the NKPA’s creation of some entirely new units. Many of the captured North Koreans could not describe to their American captors how their unit fit into the overall NKPA order of battle. Despite these difficulties, US intelligence reports during the battle presented a fairly accurate picture of the aggregate NKPA units involved. “No groups of enemy were met that were not previously known and their general positions established.” It appears that US estimates on the evolving strength of NKPA forces in the general area of the city were fairly accurate as well. A X Corps intelligence report of 21 September, which estimated 15,000 NKPA in the Seoul area, roughly matched the “more than 20,000” peak NKPA strength given in the 1st Marine Division’s after-action report, the difference from NKPA reinforcements arriving after the twenty-first.
Far less accurate were the intelligence estimates on how well those enemy forces would fight. It was true that many of the North Korean units in the Seoul area largely consisted of recently drafted students and farmers, but NKPA efforts to fortify them with experienced officers proved successful. Even after the battle, the X Corps war diary summary did not give these units proper credit, stating these “Hastily mobilized recruits did little to increase the enemy potential in the objective area.” Another X Corps G-2 section report, issued during the battle on 24 September, disagrees with this assessment by describing the resistance of these units with raw recruits as “determined.” Perhaps the X Corps war diary was reflecting the views of its commander, who underestimated the NKPA before the battle. That sort of misjudgment occurred again a few months later, as United Nations forces approached the Yalu, although with far more serious consequences.
The hasty planning cycle for the Inchon-Seoul operation put considerable strain on the intelligence organizations responsible for providing maps and other information on Seoul. While the X Corps planning staff did have 6400 highly detailed 1:12,500-scale maps of the city for distribution, not all of their maps used the same grid system, and there was no time to reprint them with the standard Universal Transverse Mercator grid. Some American engineers made their own up-to-date maps of the Inchon urban area at a 1:5,000 scale, using recent aerial reconnaissance photos. The Far East Command Intelligence Section produced a detailed terrain handbook for Seoul in mid-August, with information on the city’s road network, infrastructure, and structural patterns. Given the rapid pace of advance from Inchon to Seoul, intelligence units had difficulty delivering the relevant maps to some units, and there were reported shortages for pilots and at the regimental level. There were a few instances of units being misled by errors on maps outside the city, and one tank company became temporarily lost in the city, but such events were rare. The overall availability of maps and information on Seoul appears to have been sufficient for the needs of American forces in the city.
The belated recognition of the northwest hill mass as the NKPA main line of resistance was not solely a shortfall in intelligence or reconnaissance, but one shared with generals Almond and Smith. As early as 19 September, before the 5th Marines crossed the Han, a 1st Marine Division intelligence report mentioned the area as a Japanese and Korean training ground. On 21 September, as the 5th Marines approached the hill mass, a 1st Marine Division intelligence report characterized NKPA positions there as “apparently thin and hastily organized” and called the stronger defense of Yongdungpo evidence of it being the most critical front to the NKPA. However a photo interpretation section to that same intelligence report mentioned a “system” of trenches fortifying the hill mass. Just one day later, on 22 September, an X Corps intelligence report would call the defenses there “well-organized,” and held by at least two reinforced regiments with the intention of holding their positions. Two days later, on 24 September, the 1st Marine Division called the hill mass the enemy’s main line of resistance. Smith and Almond, given the location of the hill mass and its previous use for training, should have deduced an alternative to a frontal assault in case the need presented itself. US intelligence personnel did not predict the “just in time” arrival of the NKPA forces to the hill mass, although such a reaction was sufficiently obvious that both Almond and Smith should have accounted for it in their plans.
Almond also erred when he concluded prematurely, late on 25 September, that the NKPA was fleeing the city. Just before dusk on 25 September, US aircraft reported columns of NKPA streaming northward out of the city, and Almond’s G-2 section stated in its report for that day, “Remnants of the defeated enemy appeared to be withdrawing to the north and east of the city.” Previously, on 24 September, the 1st Marine Division issued a report stating that, according to an informant, the NKPA was pulling out its regular forces and replacing them with “student volunteers.” The next day another 1st Marine Division report cited civilian accounts of NKPA movement out of the city, and prisoner of war reports that few NKPA remained in Seoul. However, missing were any corresponding reports from the Marine regiments in the city of a similar retreat. Any underestimation of the NKPA’s ability to mount effective delaying actions should have been purged from Almond’s mind after the 5th Marine’s four-day fight for the northwest hill mass. The next day, 26 September, the X Corps G-2 section reports changed their tone to use words such as “determined” and “stubborn” in reference to the NKPA units still in the city.
Air reconnaissance was an important element in the US collection apparatus. US intelligence units did not complete the first “photo mosaic” of the Inchon to Seoul area, in 1:25,000 scale, until two days after the Inchon landings. The tasking of photo reconnaissance missions fell behind the initial advance of the forces moving out from Inchon, but Seoul’s status as the main objective meant it was the target of many sorties. Photo analysts reported approximately 250 targets in the city to the Fire Support Coordination Center. The principal shortfall in photo reconnaissance was the time required from request to delivery, a minimum of seventy-two hours. In addition to photo reconnaissance, 720 visual reconnaissance flights were flown in the Inchon-Seoul operation. However, the light aircraft primarily used for this mission were in short supply, vulnerable to ground fire, and needed for liaison duties. The vulnerability of the light aircraft was exacerbated by the need to fly low (often under 2500 feet) so that well-camouflaged NKPA targets could be acquired. Making the task for US aerial observers easier were the obvious general locations of NKPA positions, as given away by the street barricades.
Other significant sources of intelligence on the NKPA were North Korean prisoners and civilians. Captured NKPA soldiers were a major source, with both X Corps and 1st Marine Division intelligence reports heavily seeded with references to information generated from interrogations. Civilians, sometimes walking for miles, passed on the locations of enemy forces, weapons and ammunition caches, and NKPA movements. While generally accurate, their reports did tend to exaggerate enemy numbers. Captured documents were sometimes a source of information, but it was apparent to US intelligence personnel that the NKPA had been careful to leave little documentation behind as they retreated.
Without the help of R.O.K Officers on battalion level tactically information from prisoners, natives and documents would have been non-existent.
One important shortfall was noted in the 1st Marine Division’s after-action report: “The art of reconnaissance patrolling was a largely lost art.” While the first 5th Marine patrol sent across the Han failed to discover the NKPA on the far bank, a patrol from the 1st Marines did give critical warning of the impending attack in Seoul on the night of 25 to 26 September.
The skill with which the North Koreans employed camouflage made reconnaissance and surveillance more difficult for US forces. US military police set up checkpoints to screen out North Korean soldiers in civilian clothes moving with the refugees, while attached ROK police proved invaluable at these checkpoints as they could spot hiding North Koreans and “Without doubt saved the lives of considerable American soldiers.”