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Overview of the Korean War

Korean War HistoryAdvance, Retreat, & Stalemate: A limited war in the nuclear age.

“By its participation in the Korean conflict the Army of the United States, in a determined effort to restore international peace and security, has been for the first time committed to battle under the flag of the United Nations.  Confronted by most arduous conditions, the American soldier has fought with traditional bravery and skill against Communist aggression in Korea.  He has met every test with honor.” - J. Lawton Collins, U.S. Army Chief of Staff, August 16, 1949 - August 15, 1953

“The men who make history have no time to write about it.” - Prince Klemens von Metternich (1773 - 1859)

Fortunately, 19th century Austrian statesman Metternich was to be proven wrong in the century following his death.  In fact, Gen. Collins’ praise for the American soldier cited above appears as an introduction to a two volume historical examination that was prepared and published by the Department of the Army in the period during and immediately following the Korean conflict.  Unlike some subsequent conflict histories that were compiled long after the fact, the two Department of the Army volumes, republished by the Army’s Center of Military History in 1988-89, provide modern readers with an accurate and time-appropriate framework for examining the subject of both Army and Marine Corps ground operations during the Korean War.

For most historical purposes, the start of the U.S. ground war experience in Korea is generally marked from President Truman’s June 29, 1950 authorization for Gen. Douglas MacArthur to commit ground troops to blunt communist aggression from the north.  Korean War ground actions went on to span three years, one month, and two days, “officially” ending with the signing of the cease-fire on July 27, 1953. 

The two government volumes identify 13 distinct phases to the Korean War ground operations during this period.  The initial volume identifies four primary phases of ground war operations during 1950: Withdrawal to the Pusan Perimeter (June 25 - July 31); Defense of the Pusan Perimeter (August 1 - September 14); UN Counteroffensive (September 15 - November 24); and Withdrawal from the Yalu (November 25 - December 31).  The second volume of the series goes on to identify nine more phases to the ground conflict: Enemy High Tide (January 1 - 24, 1951); Attack and Counterattack (January 25 - February 28, 1951); Crossing the 38th Parallel (March 1 - April 21, 1951); Enemy Strikes Back (April 22 - May 19, 1951); UN Resumes Advance (May 20 - June 24, 1951); Lull and Flare-up (June 25 - November 12, 1951); Stalemate (November 12, 1951 - June 30, 1952); Outpost Battles (July 1 - December 31, 1952); and The Last Battle (January 1 - July 27, 1953).

Drawing primarily on the Department of the Army history, this article offers a broad overview of the units committed and types of operations conducted during each general phase of ground operations on the Korean peninsula.

"The rapidly disintegrating battlefield situation prompted a decision by MacArthur to begin the commitment of U.S. ground elements in a 'piecemeal' fashion, beginning with one half of a battalion combat team from the 21st Infantry Regiment of the U.S. 24th Division."

At the time of the initial invasion, U.S. ground force strength was comprised of 10 U.S. Army divisions and a U.S. Marine Corps division, with a large percentage of this capability still “under strength” from the post-WWII demobilization process.  Moreover, it was a full five days after the U.S. government received official notification of the North Korean invasion south across the 38th Parallel that President Truman authorized General MacArthur to commit U.S. ground forces in Korea.  The South Korean capital had already fallen to the communists the day prior, leaving behind a rapidly eroding political and military climate for the introduction of troop units.  As a result, the opening stages of the ground war in Korea involved the commitment of U.S. troop units into a combat action that was already withdrawing south down the Korean peninsula toward what would come to be called the Pusan Perimeter to signify its enclosure of the UN supply port at Pusan.

The rapidly disintegrating battlefield situation prompted a decision by MacArthur to begin the commitment of U.S. ground elements in a “piecemeal” fashion, beginning with one half of a battalion combat team from the 21st Infantry Regiment of the U.S. 24th Division.  Known as Task Force Smith, the unit was transported to Korea by air during July 1-2, and immediately charged north by rail and truck to face incredible odds against the North Korean military onslaught.  Meeting an entire division of North Korean armor and infantry on July 5, the partial battalion of U.S. infantry held their ground for seven hours before withdrawing back through other elements from the 24th Division that had followed the task force to Korea. 

The initial plan tasked the 24th Division with fighting a delaying action while additional reinforcements were shipped from Japan and, eventually, the United States.

Next to arrive was the 25th Division, which began crossing from Japan on July 9, and the 1st Cavalry Division (Infantry), which disembarked from its ship convoy nine days later.  They were joined about a week later by the separate 29th Regimental Combat Team (RCT).  By the end of the month, all of these units were concentrated in a foothold protecting Taegu and Pusan at the southeastern corner of the peninsula.

The subsequent six week defense of that foothold marked the second major phase of the ground war in Korea.  The period included the arrival of three more large contingents of U.S. reinforcements: the 2nd Division from the United States; the 5th RCT from Hawaii; and the 1st Provisional Marine Brigade (advance component of the 1st Marine Division) from the United States. To assist in the reinforcement of depleted U.S. forces, August also saw the initial integration of South Korean nationals into U.S. Army company-sized units.

Representative of the combat activities during this period were the actions of  Task Force Kean, consisting of elements of the 25th Division, the 1st Provisional Marine Brigade, and a Republic of Korea (ROK) battalion.  The task force was thrown against the North Korean 6th Division, which had been massing in the mountains on the left flank of the perimeter prior to an assault on Pusan.  The UN counteroffensive opened on August 7, and was supported by Marine, Navy, and Air Force aircraft.  The four-day action was characterized by point blank artillery missions and extensive North Korean infiltration of UN lines, but by August 11, the task force had secured the left flank of the Eighth Army and forced North Korean withdrawal from many of their now tenuous salients.

Korean War History

Similar combat actions took place at other locations along the front, all featuring stories of amazing heroism on the part of UN ground forces.  The situation was far from a stalemate, as evidenced by places like Sobuk Ridge (“Battle Mountain”) that changed ownership more than a dozen times in less than a month.

One feature of Korean War land operations that jumps from the pages of the history compiled at the time was the frequent and painful infiltration of U.S./UN lines by “enemy soldiers in civilian clothes,” an aspect of Communist warfare that was clearly a new experience for most U.S. personnel.

Nonetheless, the actions undertaken by the U.S. and a growing array of allied forces in defense of the Pusan “beachhead” clearly demonstrated the ability of UN forces to counterattack, an opportunity that was exploited on a grand scale in mid-September when the recently-activated U.S. X Corps (comprised of the 1st Marine Division and 7th Infantry Division) made a surprise amphibious landing at Inchon.  The September 15 landing provided the opportunity for the Eighth Army to attack out of their beachhead perimeter.  The Eighth Army was now composed of two ROK corps and two U.S. corps, the latter units featuring participation by the 27th British Commonwealth Brigade and additional attached ROK units.

The perimeter was steadily expanded against often fierce resistance.  By September 26, however, a unit of the 1st Cavalry’s 70th Tank Battalion had raced ahead through enemy positions to join forward elements of the 7th Division that had fought southeast from Inchon.  Meanwhile, the capital, Seoul, was officially returned to friendly hands the same day.  A continuing retreat by Communist forces led to the crossing of the 38th parallel by initial ROK elements on October 1, with U.S. and Commonwealth troops quickly moving over to bring the war to North Korean soil.

After capturing Seoul and Suwon, the X Corps had been withdrawn from combat to prepare for a second amphibious landing on the east coast, again behind enemy lines, at the North Korean port of Wonsan.  However, the rapidity of the North Korean retreat translated to an October 26 administrative landing by the 1st Marine Division at Wonsan and an October 29 landing by the U.S. 7th Division with ROK supplement 178 miles north at Iwon. 

While the U.S. IX Corps and ROK III Corps stayed in South Korea to destroy pockets of bypassed resistance, the U.S. X Corps and Eighth Army (now supplemented by a Turkish Brigade) continued their drives in the north.  By the fourth week of October, elements of the U.S. 7th Division were looking across the Yalu River into Manchuria.  UN forces prepared for a final push, with the Eighth Army operating west of the mountains and the X Corps to the east.

Although elements of approximately a dozen Chinese divisions had been encountered by UN forces during early November, it was still not clear to many UN planners whether these units represented volunteer supplements or a much larger scale commitment.  That position was painfully clarified on November 25 when two Chinese field armies struck from across the Yalu in an attempt to pin the two major UN forces against each coast while additional Communist forces moved south.

The Eighth Army was forced to withdraw by land, with division elements fighting costly but vital delaying actions that allowed the formation of a new defensive perimeter below the 38th parallel, north and east of Seoul, by mid-December.  Meanwhile, from their positions deep in northeast Korea, the X Corps began actions that would lead to withdrawal by land and sea.

The 1st Marine Division had actually been preparing to attack northwest from their positions near the Changjin (Chosin) Reservoir in an effort to ease the pressure on the Eighth Army’s eastern flank.  However, on November 27, six Chinese divisions attacked the Marines and two nearby battalions of the 7th Infantry Division from their positions in the mountains surrounding the reservoir.  After consolidation near Hagaru-ri, the consolidated U.S. units were forced to painfully fight a route all the way to the coast through vicious Chinese attacks while also dealing with the misery of a frozen winter that ranks with the historical American heroism of Valley Forge.  Marine Corps histories note that the division’s reservoir breakout operations were supplied by Navy, Air Force, and Marine Corps aircraft that also succeeded in evacuating several thousand casualties. 

After two weeks of these combat operations, the Marines, with their Army attachments, joined other X Corps units consolidated around the port of Hungnam, where they were evacuated by sea between  December 11-25, 1950.

With UN forces now defending a line generally running along the 38th parallel, the new year was greeted by a massive Communist assault.  Although forces were deployed along the entire line, the assault thrust was in the west and center sectors with seven Chinese armies and two North Korean corps penetrating toward Seoul and Wonju. 

UN forces were again reluctantly ordered to withdraw, evacuating both Seoul and its port of Inchon in the face of the combined Chinese and North Korean attack.  After reaching new defensive lines, UN forces began to assess the tactical picture through “reconnaissance in force” operations with infantry, armor, field artillery, and engineer units operating together as combined arms organizations. 

I Corps was one of the first major units to perform these operations, dubbed Operation Wolfhound.

The success of Wolfhound led to Operation Thunderbolt, a northward assault by seven parallel columns from the UN I and IX Corps that began on January 25, 1951.  Of the seven columns involved in the new attack, only the Turkish Brigade east of Osan encountered what would later be termed “stiff opposition.”  Enemy POWs later reported that an entire 30-mile Communist front had been screened by just two divisions of the Chinese 50th Army.

Communist resistance grew by each northward mile, however, and in less than a week Thunderbolt elements had engaged at least five more Chinese divisions and two North Korean divisions in what was frequently categorized as hand-to-hand combat as they moved through consecutive phase line positions. In addition to reclaiming significant areas of terrain, Thunderbolt was notable as the first time that the Eighth Army had been able to maximize the effects of both armor and artillery in support of an advance.  The effectiveness of this weapon combination is cited as one reason for a continual stiffening of enemy resistance as the I and IX Corps moved back up to the Han River.

Similar advances followed on February 5, with the X Corps and ROK III Corps moving north under Operation Roundup.  Among the many acts of heroism encompassed by Roundup was a battle of February 13, when a battalion from the U.S. 2nd Division and a French battalion held a pivotal village for three days against counterattack by three Chinese divisions.

"Beginning with an attack by three Chinese armies, the month-long Communist offensive relied on so-called “human wave” infantry tactics supported by little artillery, very few tanks, and no air cover."

On February 21, IX and X Corps began a general northward advance under the name Operation Killer.  As part of this operation, the 1st Marine Division was removed from its extensive actions against roving North Korean guerrilla bands – units that had eliminated the concept of “rear areas” – and committed as part of the IX Corps.  Advances were slow but continual and, by the end of the month, the UN front had been stabilized on a line about halfway between the 37th and 38th parallels. 

UN planners sought a new line, just south of the 38th parallel, and began Operation Ripper on March 7 with what was possibly the largest artillery preparation of the war.  In spite of small unit delaying tactics across the front, Ripper succeeded in retaking Seoul, with all elements achieving their new positions by month’s end.  It was also about this time that UN intelligence reports positively identified an opposing force structure now consisting of nine Chinese armies (tentatively identifying 10 more), 18 North Korean divisions, and six separate North Korean brigades. 

Operation Rugged was kicked off against this opposition on April 5, 1951.  Rugged was intended as a general advance to commanding terrain located north of the 38th parallel with the hopes of occupying these positions prior to an expected “spring offensive” by the Communists. Although President Truman relieved MacArthur of all commands – replacing him with Gen. Matthew Ridgway – less than a week into Rugged, most units were positioned and prepared when the anticipated counteroffensive began on April 22.

Beginning with an attack by three Chinese armies, the month-long Communist offensive relied on so-called “human wave” infantry tactics supported by little artillery, very few tanks, and no air cover.  Initial attacks achieved some success against the ROK 6th Division in the IX Corps area, prompting a front-wide pull-back to near the previous UN phase line of March 31. Notable combat actions during this period included extreme heroism by the 1st Battalion, Gloucestershire Regiment, British 29th Brigade, which held for several days before a small number of survivors were able to reach the new UN line. 

Following success in some minor UN counterattacks, the Communists resumed their assault on the night of  May 15-16, when 21 Chinese divisions and three North Korean divisions struck down the center of the peninsula against the U.S. X and ROK III Corps.  In just one example of how this attack was slowed and blunted by the UN combined arms team, the U.S. 38th Field Artillery Battalion reported firing 12,000 105 mm artillery rounds in support of the 2nd Division in just 24 hours.

Additional Communist attacks were blunted over the next few days and by May 20, the UN forces prepared to regain the initiative.  The general advance, which included Operation Piledriver, achieved most of its objectives by mid-June, the late-month exception being a violent engagement by the 1st Marine Division in the “Punchbowl Area” north of Inje.

It may have been reflective of these latest UN ground campaign successes that the Soviet UN delegate in New York City first raised a proposal for cease-fire discussions on June 23, 1951.  

With neither side anxious to initiate major offensives with peace talks in progress, the ground war entered a “lull” phase of battalion and regimental attacks designed to consolidate positions or seize the most favorable local terrain. Unfortunately, there were exceptions to this general lull. Following a suspension of truce negotiations in late August, UN forces, including the 1st Marine Division and 2nd Division, engaged in extremely bloody battles in and around the Punchbowl region located east of the so-called “Iron Triangle.” Place names like “Bloody Ridge” and “Heartbreak Ridge” still stir memories of hard-fought victories against entrenched enemy forces.

Early October actions saw a UN advance by five divisions across a 45 mile front. In addition to protecting a rail line to Seoul, the four-mile advance may have also contributed to an enemy willingness to renew negotiations in October.

The close of 1951 saw Korean War ground operations generally return to the types of small patrols and raids that had characterized the early summer. The primary reason for the return to small scale misery and heroism was Ridgway’s decision to halt offensive ground operations. His November 12 directive allowed limited attacks to strengthen the line of resistance and to extend an outpost line a short distance further north. 

This period, until the middle of 1952, was also marked by the rearrangement of units on both sides of the front.  Battles were small but intense, with the 45th Division’s (the first National Guard division to fight in Korea) Operation Counter supported by 43,600 rounds of mortar and artillery fire during a 48-hour operation to establish a new line of secure patrol bases.

The second half of 1952 included a series of continuing small-scale attacks on both sides of the line. The increasing attack tempo on the Communist side actually began in May and culminated during October in some of the heaviest combat in more than a year. The battles showed that the Chinese had refined their use of artillery fire, with 93,000 rounds falling on UN positions across the front during October 7 alone.

The year 1953 began with continuing patrol clashes during January and February but heated up in March when the enemy began action against holders of real estate with numerical names like Hill 355, 266, 255, and 191. The objective names are indicative of the small ground gains that were sought, achieved, or lost at the cost of hundreds of lives. This “Last Battle” period had fighting as bloody as any action seen to date.  In one March 10 example, two raiding platoons from the Colombian Battalion were caught in a fire fight with the Chinese that cost them 19 men killed, 44 men wounded, and 8 men missing.

After a brief return to calm in April, the imminent signing of the cease-fire agreement apparently prompted the Chinese to strike and occupy a number of outposts along the western section of the line. The largest ground gains, however, came in the central front section occupied by the ROK II Corps. There, the official histories note that the communists succeeded in pushing 15,000 yards of the front back for 4,000 yards. 

Communist activity went into a frenzy in the days prior to agreement of cease-fire points by all sides on 19 July 19 (signing on July 27) but their losses were tremendous. UN estimates place the Communist’s July losses alone at 72,000 men, 25,000 of whom were killed.

A ground war that started out being measured in miles ended up being measured in yards. But regardless of those measurements, the human toll remains uncountably high to this day. 


Gourley, Scott R. Advance, Retreat, & Stalemate: A Limited War in The Nuclear Age

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