Although elements of approximately a dozen Chinese divisions had been encountered by U.N. forces during early November, it was still not clear to many U.N. planners whether these units represented volunteer supplements or a much larger-scale commitment. That position was painfully clarified on Nov. 25, when two Chinese field armies struck from across the Yalu River in an attempt to pin the two major U.N. 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, X Corps began actions that would lead to withdrawal by land and sea.

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.

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 Nov. 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 Dec. 11-25, 1950.

With U.N. 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.

U.N. 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, U.N. 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.

Enemy POWs later reported that an entire 30-mile communist front had been screened by just two divisions of the Chinese 50th Army.

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 U.N. I and IX Corps that began on Jan. 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 Feb. 5, with X Corps and ROK III Corps moving north under Operation Roundup. Among the many acts of heroism encompassed by Roundup was a battle of Feb. 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.

It was also about this time that U.N. 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.

On Feb. 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 U.N. front had been stabilized on a line about halfway between the 37th and 38th parallels.

U.N. 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 U.N. 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 Truman relieved MacArthur of all command – 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 U.N. phase line of March 31. Notable combat actions during this period included extreme heroism by the 1st Battalion, Gloucestershire Regiment, British 29th Brigade (the Glosters), which held for several days before a small number of survivors were able to reach the new U.N. line.

In just one example of how this attack was slowed and blunted by the U.N. 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.

Following success in some minor U.N. 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 U.N. 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 U.N. 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 U.N. ground campaign successes that the Soviet U.N. 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, U.N. 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 U.N. 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 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 U.N. positions across the front on Oct. 7 alone.

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 Nov. 12 directive allowed limited attacks to strengthen the line of resistance and to extend an outpost line a short distance farther 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 Army 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 U.N. positions across the front on Oct. 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 eight 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.

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.

Communist activity went into a frenzy in the days prior to agreement of cease-fire points by all sides on July 19 (signing on July 27) but their losses were tremendous. U.N. estimates place the communists’ 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.

This article was first published in The Forgotten War: 60th Anniversary of the Korean War.