Photo By Erin Thompson | Map of UN forces in the west and central zones during Operation RIPPER, March 1951... read more read more
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On Mar. 15, 1951, United Nations forces reclaimed Seoul for the final time during the Korean War. Intelligence played an essential role during operational planning and in the eventual recapturing of the city, as well as securing it after the fact.
Operation Ripper was developed by U.S. Eighth Army commander Lt. Gen. Matthew B. Ridgway to destroy enemy forces and equipment, recapture Seoul, and secure the area below the 38th parallel against a potential enemy offensive. In the leadup to the operation, Lt. Col. James C. Tarkenton, Eighth Army G-2, closely monitored Chinese positions near Chuncheon, northeast of Seoul and just south of the 38th parallel. Intelligence reports from behind enemy lines and prisoner of war interrogations in early March provided evidence of a possible Chinese offensive into the Eighth Army’s central zone, while North Korean forces were approaching from the northwest. Tarkenton advised Ridgway to launch Operation Ripper before enemy forces could be properly organized for a counterattack.
The operation began on Mar. 7, 1951. Ridgway kept the enemy distracted with amphibious demonstrations, staged landings, and bombing campaigns along the east and west coasts. During the operation’s first phase, UN forces moved into position along Line Albany in the I, IX, and X Corps zones, south of Hongcheon and just east of Seoul. They faced moderate resistance, but most corps elements were in position between Mar. 11-13. Ridgway approved the second phase to begin the following morning, which called for the IX Corps to advance to Line Buffalo in the I and IX Corps zones and seize key terrain at Hongcheon.
At the same time, intelligence indicated an enemy buildup north of the IX Corps area of operations, and Tarkenton was concerned about the North Koreans surrounding Seoul on the Han River and the growing threat of a counterattack near Hongcheon. His intelligence was somewhat flawed. Eighth Army had struggled to accurately identify and locate the numerous Chinese and North Korean units moving across the 38th parallel between February–March, and intelligence staff had missed entire corps and divisions in their order of battle estimates, meaning a much larger enemy force was massed around the operational area. Fortunately for Tarkenton and Eighth Army, UN operations over the previous months had diminished enemy unit strengths. While these forces were assembling for a counteroffensive, they were hardly battle-ready and were not prepared to strike in mid-March.
Based on Tarkenton’s belief the Chinese would strongly defend Hongcheon, Ridgway ordered the IX Corps to envelope the town rather than take it by frontal assault. On Mar. 14, the corps captured Hongcheon against unexpectedly light opposition. Based on the relative ease with which the city fell, Ridgway was determined to retake Seoul. Aerial reconnaissance and patrols of enemy positions on the Han River indicated the North Koreans were retreating northwest. The Republic of Korea (ROK) 1st Division entered Seoul on Mar. 14 while the U.S. 3rd Division patrolled the city’s perimeter, searching for any signs of enemy resistance. The next day, Seoul was officially occupied by UN forces. It would never again fall into enemy hands.
With phase two completed and Seoul recaptured, Operation Ripper continued into the third and fourth phases. The IX Corps moved to Line Cairo and surrounded the enemy supply hub at Chuncheon, before securing the town and moving into its final position along Line Idaho. By the end of March, UN forces were in position just below the 38th parallel.
Meanwhile, the Army Counter Intelligence Corps (CIC) was tasked with providing security and counterintelligence support to occupation forces in Seoul. On Mar. 16, a special task force of twenty-five volunteers from the 3rd, 201st, 308th, and 441st CIC Detachments entered the city and began screening for subversive elements and security threats and even helped locate and destroy enemy mines. I Corps commander Maj. Gen. John W. O’Daniel later praised the agents for the “rapid reduction of the numerous intelligence targets and the wealth of valuable intelligence data obtained…in the face of numerous hazards and difficulties” which was “a credit to every member of the task force.”
Article by Erin E. Thompson, USAICoE Staff Historian. New issues of This Week in MI History are published each week. To report story errors, ask questions, request previous articles, or be added to our distribution list, please contact: TR-ICoE-Command-Historian@army.mil.
| Date Taken: | 03.13.2026 |
| Date Posted: | 03.13.2026 15:46 |
| Story ID: | 560532 |
| Location: | US |
| Web Views: | 78 |
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