Seoul—September 1950 Part I

General Douglas MacArthur’s bold Inchon landings on 15 September 1950 were but a means to an end. The true objective of Operation CHROMITE was Seoul, as its capture would simultaneously cut off the bulk of the North Korean People’s Army (NKPA) in the south from its primary supply hub and its principal escape route back north. An added incentive, especially for someone with MacArthur’s flair for publicity, was the notoriety of recapturing an allied capital city.

Most of the defenders of Seoul were North Korean units that had been recently assembled, with little experience or training for the rank and file. Some of these units were leavened with experienced officers, and a few other units rushed up from the south. However, the caliber of most of these defending forces was not the same as those NKPA units that had crossed the 38th parallel four months earlier.

Unlike Aachen and Manila, which involved forces seasoned by several years of war, US forces at Seoul were a hastily assembled collection of units that included some personnel with World War II combat experience, but many without. Another difference from the two World War II battles was the reduced level of effort by US commanders to seal off the city. Unlike the combination of skill and luck that allowed American forces to avoid the primary enemy defensive positions guarding Aachen and Manila, the primary American thrust into Seoul would run headlong into the primary NKPA defensive position holding it.

However, the essence of the military problem was the same: a major urban area that needed to be captured from enemy forces. The particulars stressed the American military’s urban combat capabilities in some new ways, although the core objectives were the same: capture of the city in a timely manner and at a reasonable cost. The battle for Seoul would give insights into how the US Marine Corps could perform in a major urban battle and the degree to which lessons were learned from World War II.

Operational Context

As Commander-in-Chief Far East Command, MacArthur saw August 1950 as time for a bold and decisive counterblow in Korea, one he thought should happen at Inchon. In its attempt to push the United Nations forces off the peninsula, the NKPA had driven most of its forces deep into the south, leaving only scattered rear area units to guard the lines of communication needed to support those southern forces. Inchon was the second largest port in Korea, second only to Pusan, and more importantly, it was only twenty miles from Seoul. Seoul was the key because it was the rail and road hub for central Korea, and MacArthur called its capture “the primary purpose” of the Inchon landings. Most of the north-south and east-west railroads and highways went through the city. MacArthur planned to follow up the surprise landing at Inchon with a rapid advance on Seoul. Its recapture would make the North Korean deployments in the south unsustainable, and better yet, offer the possibility of cutting them off and destroying them completely. Furthermore, Kimpo airfield, between Inchon and Seoul, was the best in all of Korea.

Gathering the needed troops for the landings was challenging for a US military that just a few months earlier had been on a peacetime footing. MacArthur set up a new organization for the landings that was independent from the other forces in Korea: X Corps. He assigned his own chief of staff, Maj. Gen. Edward Almond, as commander. X Corps’ headquarters became operational on 31 August, just fifteen days before the landings. The United States Marine Corps (USMC) was the primary supplier of ground forces for this amphibious assault. The 1st Marine Division was composed of the 5th Marine Regiment (already in Korea), the 1st Marine Regiment (assembled in the United States) under the command of the legendary Col. Lewis “Chesty” Puller, and the 7th Marine Regiment (assembled from Marine units in and out of the United States). In addition to this core of three infantry regiments, the 1st Marine Division had an artillery regiment (11th Marine Artillery Regiment), a tank battalion (1st Marine Tank Battalion) and assorted other units. MacArthur augmented these Marine forces with the Army’s 7th Infantry Division, to cover the southern flank of the drive on Seoul, and two South Korean regiments.

The Inchon landings began on the morning of 15 September, with elements of the 1st and 5th Marines, and the largest naval force assembled since World War II: four aircraft carriers, two escort carriers, six cruisers, and thirty-three destroyers. While there were some modest difficulties with locating landing beaches and friendly fire, the landings were a success, perhaps exceeding even MacArthur’s expectations. Despite considerable risk, MacArthur’s plan to assault directly into a city paid off, as on day one US forces held a major port facility.

The drive inland was rapid for the first several days, beginning to cross the approximately twenty miles separating Inchon from Seoul. NKPA resistance was scattered and disorganized. The North Koreans mounted a few significant counterattacks, but these were either broken up by US air attacks, or impaled on the defensive positions Marine units set up nightly as they halted. The 5th Marines advanced eastward in parallel with the 1st Marines, with the latter to the south, advancing along the Inchon–Seoul highway. In these first few days both carrier-based aircraft (Marine and Navy) and naval gunfire support greatly aided the advance. Halfway to Seoul, before crossing the Han River, the 5th Marines angled to the northeast, securing Kimpo airfield by the morning of 18 September. Kimpo would prove key to subsequent operations, as a forward base for close support aircraft and for flying in supplies directly from Japan. After capturing Kimpo, the 5th Marines pushed on to a crossing point on the Han, approximately eight miles northwest of Seoul. They crossed on the morning of 20 September, in amphibious tractors (LVTs), amphibious trucks (DUKWs), and motorized barges, and then turned southeast toward Seoul.

The first major hurdle for the 1st Marines was an industrial suburb of Seoul called Yongdungpo, located to the southwest of Seoul itself, with the Han River in between. The Marines dealt with it separately from the rest of the city, taking the suburb in heavy fighting over 21 and 22 September that required all three battalions of the regiment. Between Yongdungpo and Seoul were the remains of three bridges across the Han, but each was heavily damaged so they were not a viable entrance into the city. On 24 September the 1st Marines crossed the Han just north of Yongdungpo, and then pivoted right to form up on the right flank of the 5th Marines for the drive into Seoul.

The 5th Marines had encountered even stronger resistance northwest of Seoul, in a string of hills shielding the northwestern edge of the city, where the NKPA had chosen to place its main line of resistance. Marine after-action reports praised the quality of the NKPA field fortifications on these hills, and the tenacity with which the North Korean forces held their ground. Even with heavy air and artillery support (naval gunfire support now being out of range), and several battalions of Korean marines, the 5th Marines needed four days to clear the hill mass. Losses for the 5th Marines were heavy, and the hills would not be fully cleared until 25 September. The ferocity of the fighting was evident in the experience of one Marine infantry company, which suffered 178 casualties out of 206 men in one day. The few men remaining succeeded in taking a ridge covered with dead North Koreans. They stopped counting bodies when the number reached 1500. The commander of the 5th Marines, Lieutenant Colonel Raymond Murray, described the battle for that high ground as more difficult than the fighting in Seoul. “Once we got past those two hills, we didn’t have all that much difficulty in the city itself.”

Around this time the two supporting drives of the operation came into play. The 7th Infantry Division’s (US Army) 32nd Infantry Regiment and the 1st Marine Division’s 7th Marine Regiment both arrived in Inchon several days after the initial landings, simply because they were not available earlier. While roughly equal in size to the two USMC regiments driving on the city itself, planners decided their later arrival better suited them for supporting roles. The mission of the 32nd Infantry Regiment was to relieve the 1st Marines south of the Inchon–Seoul highway and guard against any NKPA thrusts northward from the Pusan perimeter, sealing off Seoul from the south. Planners recognized that once the threat to Seoul became clear, the NKPA might drive northward toward Seoul with significant forces. By 24 September the 32nd Infantry had cleared the south bank of the Han immediately below Seoul. The 7th Marines crossed the Han on 23 September at the same point as the 5th Marines. The 7th Marines then drove due east, across the hills north of Seoul, to deny that terrain as either an escape route or reinforcement avenue for the NKPA.

By 25 September all three infantry regiments of the 1st Marine Division were in a line, north of the Han, near the western edge of the city. The south bank of the Han was clear, allowing X Corps to place several artillery battalions there, ready to support operations in the city.17 Lastly, the 32nd Infantry Regiment was ready south of the city. It had taken ten days, but the final assault was set. The map gives an overview of the two Marine thrusts toward the city as of 23 and 26 September, the 5th Marines crossing the Han northwest of the city then driving southeast toward the city, while the 1st Marines drove toward Seoul through Yongdungpo. The map also shows the advance of elements of the U.S. Army’s 7th Infantry Division south of the city and southeast to link up with other US forces breaking out from the Pusan Perimeter.

As the battle for Seoul was an early battle in the Korean War, the previous experience and training of the participants were important issues. It is unclear what proportion of the US personnel had World War II combat experience, although experience level was less at the lower enlisted ranks and the first few ranks of officers. One officer in the Army’s 31st Field Artillery Battalion described “at least half” of the enlisted men below the rank of sergeant as without World War II experience. The Marines began the war with thirty fighter reserve squadrons with 95 percent of their officers with combat experience, although that was not necessarily the ratio for the pilots over Seoul. In some cases the lack of experience related to equipment. The men of the 1st Tank Battalion had only the briefest introduction to their M26 Pershing tanks, as the unit simultaneously received its orders to deploy to Korea and notice that most of its Sherman tanks were to be replaced with Pershings. Fortunately for the Marines, their air and ground units had undergone a considerable amount of training in the previous year that partially made up for the short deployment notice. The units of the Army’s 7th Infantry Division were hampered by a massive influx of untrained Korean replacements, as directed by MacArthur, with approximately half the division’s manpower being these men. While that infusion allowed the 7th Infantry Division to quickly expand, the Koreans were of dubious value with so little time for US forces to train them (in addition to the language barrier).

The Foe

The Inchon landings apparently caught the North Koreans by surprise. The NKPA units encountered by US forces in the first three days were mostly reserve and rear security forces. However, starting on 20 September, Seoul’s defenders began erecting barricades in the streets, and by the time the 5th Marines crossed the Han and the 1st Marines attacked the high ground just west of Yongdungpo, the units they encountered were ready for them.

In their scramble to find units to reinforce Seoul and its vicinity, the North Koreans drew upon uncommitted reserve units pulled up from the south, units on their way to the south but held in Seoul, recently formed units sent down from the north, and hastily assembled local units of whatever manpower they could find. Some of the NKPA units actually consisted of recently drafted South Koreans, being held in the rear until they were needed at the southern front as replacements. At the time of the landings there were 8000–10,000 NKPA in the Seoul area, which later climbed to over 20,000. As almost all of the larger combat formations were in the south surrounding the Pusan perimeter, those available for the defense of Seoul were mostly regimental-size or smaller and composed of inexperienced men. The sole division-size NKPA unit present in the Inchon-Seoul campaign was the 18th Rifle Division, which the NKPA called back on its way south. Prior to the Inchon landings, the NKPA had engineer and anti-aircraft units in Seoul. These two unit types would prove useful in the coming defense, especially the 1200-man 19th Antiaircraft Artillery Regiment.

More capable NKPA units arrived just in time to delay US forces at Yongdungpo and the hill mass northwest of Seoul (north of the Han). According to a NKPA POW the 78th Independent Regiment, one of the units that was to give the 5th Marines considerable trouble in the hills, only arrived at that main line of resistance on 19 September, just one day before the 5th Marines crossed the Han. The primary defenders of Yongdungpo, the 87th Regiment, arrived on 20 September, just as the 1st Marines were ready to attack.

The NKPA at Seoul was largely a foot-mobile infantry force, with modest armor and artillery support, but no air support. Even the more capable combat formations were short of experienced manpower, such as the 78th Independent Regiment, composed primarily of newly recruited students. These raw recruits exhibited poor marksmanship, but the plethora of Russian sub-machine guns, light machine guns, and heavy machine guns at the rifle company level allowed them to dispense heavy volumes of small arms fire.

Inexperience, however, was not the case with the officers, many of whom were veterans of China’s civil war. The Marines attributed the stout defense exhibited by many NKPA units to the triumph of fear of the officers over low morale. In one notable case, the Marines even suspected a Russian was among the NKPA officers. “Fireproof Phil” was taller and of lighter complexion than his men, and he continually exposed himself to Marine fire while rallying his troops in the hills northwest of Seoul.

The NKPA’s artillery and mortar support was the opposite of its small arms: low volume but high accuracy. The NKPA had a large number of 82mm and 120mm mortars, 76mm field guns, and a smaller number of 122mm howitzers.

The outstanding aspect of the enemy use of mortars is the accuracy with which they are employed, indicating in most cases that they kept at least one expert for each weapon and that much of their fire is observed, as is the case with their artillery.

And yet, fortunately for American forces, the North Koreans did not mass their artillery and mortar fires. One battalion of the 5th Marines noted it saw no barrage of greater than six rounds in the Inchon-Seoul campaign. The Marines surmised this was because the NKPA parceled out its artillery and mortars in small detachments to infantry units.

The anti-tank capability of the NKPA was significant on paper, but it proved grossly inadequate on the battlefield, primarily due to poor gunnery. The artillery component was mostly towed 45mm guns, towed 76mm guns, and self-propelled SU-76s (76mm gun). The 76mm guns had adequate performance against the lighter armor of the Shermans, but were insufficient against the Pershing. The infantry had satchel charges and a large number of Soviet 14.5mm anti-tank rifles. The satchel charges usually required a risky dash to within throwing distance of the target, while the anti-tank rifles had ceased being useful against anything except light armored vehicles since the early years of World War II. Mines proved the most effective NKPA anti-tank tool, although they were less effective once the Americans realized their prevalence. The weapon with the most potential was the NKPA’s own tanks. Armed with a powerful 85mm gun, roughly the equal of the Pershing’s 90mm, the T-34/85 (the only NKPA tank type encountered) had the penetration potential to deal with even the Pershing’s heaviest armor out to approximately 500 meters. The armor on this variant of the T-34 was insufficient to survive hits from the Pershing’s 90mm, however. Several NKPA tank units arrived in Seoul after the Inchon landings, although many of their vehicles were lost in counterattacks outside of the city. The last to arrive, on 23 September, had ten to fifteen tanks, making the total number in the city probably fewer than twenty.

The North Koreans were most adept at camouflage. “Outstanding in the enemy’s conduct of his defense was his ability to camouflage.” Gun emplacements and field fortifications would make good use of the terrain and natural materials. Their soldiers were also camouflaged in that most carried a set of civilian clothes with them at all times. They would don these clothes to allow for safe movement between positions, for dispersion and escape, and for the infiltration of agents and spotters behind US lines. In some cases, entire platoons put on civilian clothes and then continuing to operate as tactical units. This tactic was effective with the large number of civilians present in Seoul. There were also at least two reported instances where NKPA personnel used American clothing and equipment.

Some of the NKPA tradecraft was learned from the Chinese and Soviets. Red Army advisors had trained the NKPA in mine warfare, and US prisoners of war (POWs) reported seeing Soviet officials in Seoul the day after the Inchon landings (16 September). Prior to the landings, US military intelligence had received many reports of Soviet advisors working with NKPA units. The 1st Marines reported, “The city was undoubtedly organized under the supervision of Russian Officers.” A Chinese field fortification manual, captured by US forces from the North Koreans, had sections on urban fortification and how specifically to deal with a mechanized attacker. Also captured was a 1948 Soviet manual (translated into Chinese) titled “Tanks in Battle,” which described the defensive use of tanks in urban areas. However, the adoption of Chinese and Soviet tactics by the NKPA was limited. While they had many of the smaller details correct (such as individual camouflage), the NKPA fell short on the larger and more important issues, such as combined arms and flanking maneuvers.

On the defensive, the North Koreans did prove themselves capable of “conducting a most skillful delaying action,” both outside and inside Seoul. Their urban barricades reduced the mobility of the Marines, but they could not completely halt the advance of the Americans. NKPA fortifications were certainly extensive inside Seoul, although the degree of integration of their defensive positions is less clear. The 1st Marines reported:

Defensive positions on the outskirts of Seoul and especially in the city were extensive, well planned and mutually supporting and displaced in depth.

The reference to “mutually supporting” may be describing fortifications outside the city, but only on a local level in the city, as the same after-action report describes independent and usually isolated pockets of resistance inside Seoul.

In sum, while hardly the cream of the NKPA, the North Koreans defending Seoul exhibited selected although important areas of expertise. Their performance in fortification, counter-mobility, small unit leadership, and indirect fire support all supported their operational goal of holding Seoul as long as possible. To this point in the war, the NKPA had shown considerable skill in offensive operations, leaving their prowess in defensive warfare an unknown. The Inchon-Seoul campaign would show the NKPA to have significant defensive capabilities as well.

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