Operation Thunderbolt

Operation Wolfhound

On 15 January 1951 Ridgway ordered a reconnaissance in force by US I Corps. Ridgway warned I Corps' commander General Frank W. Milburn against permitting any situation to develop during the operation that would require additional forces to extricate those initially committed. Neither was Milburn to attempt a large scale exploitation, if that opportunity occurred, except on Ridgway's order. If all went according to instructions, Ridgway estimated, the operation would be concluded by dark on the 15th or, at the latest, on the 16th. Milburn assigned the main task to the 25th Infantry Division, instructing General William B. Kean to attack the Suwon-Osan area with an infantry regiment and a battalion of tanks supported by artillery and engineers. Kean selected as the central force the 27th Infantry Regiment Wolfhounds, from whose nickname the reconnaissance was named Operation Wolfhound. To protect the main force on the east, Milburn ordered the 3rd Infantry Division to send a smaller force of infantry and tanks to cut the Suwon-Kumnyangjang-ni stretch of the lateral Route 20 and instructed the Republic of Korea Army (ROKA) 1st Infantry Division to send a battalion as far as Ch'on-ni (37.2°N 127.2085°E / 37.2; 127.2085), on Route 17 3 miles (4.8 km) south of Kumnyangjang-ni (37.235°N 127.2085°E / 37.235; 127.2085). Ridgway notified U.S. IX Corps also to provide protection on the east, for which IX Corps' commander General John B. Coulter directed the ROKA 6th Infantry Division to station a battalion in blocking positions just east of Kumnyangjang-ni.

On the 15th the ROKA battalions reached Ch'on-ni and Kumnyangjang-ni over Route 17 without contact. The 1st Battalion, 15th Infantry Regiment, and two companies of tanks from the 3rd Division which followed the same axis to Kumnyangjang-ni received small arms and heavy mortar fire after turning west for 1 mile (1.6 km) on Route 20 toward Suwon. An exchange of fire with some 6-800 PVA held the 3rd Division force in place for the remainder of the day. Wolfhound forces elsewhere met no opposition, but were delayed by damaged roads and bridges. The bulk of the reinforced 27th Infantry moving over Route 1 in the main effort halted for the night at the northern edge of Osan. The 1st Battalion of the regiment and tanks following Route 39 near the coast stopped at Paranjang, 10 miles (16 km) to the west.

As Colonel John H. Michaelis' two columns converged on Suwon over Routes 1 and 39 on the morning of the 16th, Milburn ordered the Wolfhound forces to withdraw to the Chinwi River at 14:00. Having so far met only a few PVA, who appeared to be stragglers, Michaelis ordered a motorized company of infantry and a company of tanks from each column to sprint ahead and inflict as much damage as possible on enemy forces discovered in Suwon before withdrawing. On the left, after the tank-infantry team moving on Route 39 to Route 20 and then turning east came to a destroyed bridge 2 miles (3.2 km) southwest of Suwon, dismounted infantry continued the advance and investigated the southwestern edge of town without finding PVA/KPA forces. On Route 1 the tanks and infantry received fire from a strong PVA force deployed 0.5 miles (0.80 km) south of Suwon and from machine gunners atop buildings inside town. Michaelis' team deployed and returned the fire for a half hour, then under the cover of air strikes withdrew out of range.

The Wolfhound forces developed a Corps' outpost line along the Chinwi with a westward extension to the coast and pushed patrols back into PVA/KPA territory. Ridgway commended them, more for the offensive spirit displayed than for results achieved. Milburn estimated that the two-day operation had inflicted 1,380 PVA/KPA casualties, 1,180 by air strikes, five captured and 195 killed by ground troops, his own losses were three killed and seven wounded. The PVA captives identified three armies, but since the 27th Infantry had taken these prisoners before running into the PVA position at Suwon, the identity of the unit defending the town was obscure. Most pertinent, the reconnaissance revealed that no large force was located south of the Suwon-Kumnyangjang-ni line, but that organized groups did hold positions along it.

Having successfully concluded Wolfhound on 20 January, Ridgway instructed his Corps' commanders to devise similar operations. Milburn responded on the 22nd with an infantry-armor strike built around the 35th Infantry Regiment that in concept nearly duplicated Operation Wolfhound. Two small encounters during the one-day operation resulted in three PVA/KPA killed and one captured with no losses to the regiment. The strike confirmed the absence of strong PVA/KPA forces within 10 miles (16 km) of the I Corps front. It also raised the possibility that KPA forces were now operating south of Seoul when the captive identified his unit as the 8th Division, part of KPA I Corps.

Task Force Johnson

During the week before Ridgway issued his 20 January directive he had prodded Coulter to increase the strength, continuity, and depth of IX Corps’ reconnaissance. He also had directed Coulter to move the 1st Cavalry Division's 70th Tank Battalion from its deep reserve location near Sangju in the Naktong River valley to Chinch'on, 15 miles (24 km) behind the Corps front. From Chinch'on the tankers were to back up the ROKA 6th Infantry Division and also were to be employed in a reconnaissance in force wherever Coulter saw an opportunity. Regardless of Ridgway's dissatisfaction, Coulter was certain that his patrols had shown the IX Corps sector below the Kumnyangjang-ni-Ich’on-Yoju road to be free of any large PVA/KPA force. Since 12 January the 24th Infantry Division had kept a battalion in Yoju, and on the 21st General John H. Church dispatched another battalion accompanied by tanks and a battery of artillery to Ich'on with instructions to stay until pushed out. At the Corps' left, the ROKA 6th Infantry Division had not established outposts that far forward but had placed a battalion at Paengam-ni on secondary Route 55, 6 miles (9.7 km) short of the Kumnyangjang-ni-Ich'on stretch of Route 20.

After receiving Ridgway's instructions on the 20th, Coulter scheduled for the 22nd a one-day operation built around the 70th Tank Battalion in which his force was to push north of Route 20 between Kumnyangjang-ni and Ich'on. The 1st Cavalry Division was to mount the operation, developing and pushing the PVA/KPA in the objective area without becoming heavily engaged. General Hobart R. Gay organized a task force under the 8th Cavalry Regiment commanded by Colonel Harold K. Johnson that added infantry, artillery, and engineers to the tank battalion. Johnson was to move up Route 55 through the South Korean outpost at Paengam-ni to Yangji-ri on Route 20, then investigate east and west along the road and the high ground immediately above it. Johnson's principal engagement was an exchange of fire with an enemy company discovered on the reverse slopes of the first heights above Yangji-ri. The task force suffered two killed and five wounded, while enemy casualties were estimated at 15 killed by ground troops and 50 by air strikes. The lack of contact before reaching Yangji-ri supported Coulter's conviction that the area below Route 20 was unoccupied, while the Yangji-ri exchange supplied further evidence that organized enemy groups were located along the road.

Operation

Reconnaissance in force (9-29 January)

Ridgway wanted a clearer picture of PVA/KPA dispositions below the Han River before committing forces to general offensive operations. On 23 January his intelligence officer reported the bulk of the PVA XIII Army Group to be below Seoul in the area bounded by Route 20 on the south and the Han River on the east and north. Air reconnaissance had been reporting steady troop movements below the Han but did not confirm the presence of such a large force in that region. Nor had recent ground contacts developed any solid enemy defense at the area's lower edge. Resolving the ambiguities, Ridgway judged, required a deeper and stronger reconnaissance in force, which he scheduled for the morning of the 25th under the name Operation Thunderbolt.

In the operation Milburn and Coulter were to reconnoiter as far as the Han, each using not more than one US division reinforced by armor and, at the discretion of each Corps commander, one South Korean regiment. Each Corps' force was to establish a base of operations on the night of the 24th along a line of departure 10 miles (16 km) ahead of Line D, from the coast through Osan to Yoju, then advance to the Han in multiple columns through five phase lines about 5 miles (8.0 km) apart. To ensure a fully coordinated reconnaissance, Ridgway made Milburn responsible for ordering the advance from each phase line in both Corps' zones; to guarantee the security of the advance, he instructed Milburn to order each successive move only after he had clearly determined that no enemy group strong enough to endanger any column had been bypassed. Ridgway intended that his ground troops would have ample air support. He planned to postpone the operation if for any reason on the 25th Fifth Air Force commander General Earle E. Partridge could not assure two successive days of maximum close support. Ridgway also arranged for I Corps to be able to call down gunfire from a heavy cruiser and two destroyers of Task Force 95 stationed off Inchon.

X Corps was to protect the right flank of the Thunderbolt advance. On 23 January Ridgway had his deputy chief of staff, Brigadier general Henry I. Hodes, deliver instructions to General Edward Almond requiring X Corps to maintain contact with IX Corps at Yoju and to prevent enemy movements south of the Yoju-Wonju road. Almond, as he had been instructed three days earlier, also was to send forces in diversionary forays north of this road.

On the 24th Ridgway reconnoitered the objective area from the air with Partridge as his pilot. The two generals flew low over the territory 20 miles (32 km) ahead of the I and IX Corps fronts for two hours, but saw no indications of large enemy formations. Although this flight did not conclusively disprove the current intelligence estimate, Ridgway was more confident that his forces would reach the Han, and he also saw possibility of holding the ground covered. That night, from a forward command post established at I Corps headquarters in Cheonan, he ordered Milburn and Coulter to prepare plans for holding their gains once their forces achieved the fifth phase line stretching eastward from Inchon. The two Corps' commanders completed these plans on the 25th. Thus the Thunderbolt reconnaissance tentatively assumed the nature of a general attack within a few hours after it started.

General advance (30 January-4 February)

Ridgway in the meantime converted his reconnaissance in force to a full-fledged attack. On the 30th, although his assault forces were some distance short of the fifth phase line, where he originally had planned to establish the remainder of I and IX Corps, he authorized Milburn and Coulter to bring their remaining units forward from Line D to hold the ground that had been gained. He did not release these forces for commitment in the advance, but he did take steps to ease the progress of the attack by instructing Milburn to plan a strong armored thrust through the coastal lowland on the west flank. Beyond this, he directed his operations officer to arrange a maximum air effort to isolate the battlefield south of the Han. He also began to widen the offensive. On the 30th he asked Almond and the ROKA chief of staff, General Chung Il-kwon, for recommendations on sending the X Corps and the ROKA III Corps forward in the fashion of Operation Thunderbolt. The purpose of the advance, he explained, would be to disrupt the KPA II and V Corps, which were still regrouping east of Route 29. On 2 February he ordered the ROKA I Corps to join the advance. The South Koreans were to move as far north as the east coast town of Gangneung.

When executed, the instructions Ridgway issued at the turn of the month would set the entire Eighth Army front in forward motion. In terms of ground to be gained and held, however, Ridgway intended that this carry his forces no farther than the lower bank of the Han in the west and a general line extending eastward from the Han River town of Yangp'yong through Hoengsong in the center of the peninsula to Gangneung on the coast. Only if PVA/KPA forces elected to withdraw above the 38th Parallel would he consider occupying a defense line farther north, and in this context he asked his staff near the end of January for recommendations on the most advantageous terrain lines for the Eighth Army to occupy during the spring and summer months. Otherwise, his current judgment was that the ground farther north, to and including the 38th Parallel, offered no defensible line worthy of the losses risked in attempting to take it. In limiting the Eighth Army's defense line in the west to the lower bank of the Han, Ridgway excluded Seoul as an objective. Occupying the city, in his estimation, would provide no military advantage but would, rather, produce the disadvantage of placing a river immediately in rear of the occupying forces. He had in fact directed his staff to prepare plans for crossing the Han and capturing the city. But, in line with his views, these plans were not to be carried out unless there arose an opportunity to destroy a major enemy force in which the retaking of Seoul was an incidental possibility. In any event, Ridgway entertained no thought of a prolonged effort to hold any line. Knowing that there would be no major reinforcement of the Eighth Army and assuming that enemy forces would keep trying to drive the Eighth Army out of Korea or destroy it in place, he saw no wisdom in accepting the heavy attrition that a static defense seemed certain to entail. In sum, he considered the permanent acquisition of real estate an impractical, if not unachievable, objective. In his mind, inflicting maximum losses on the Chinese and North Koreans, delaying them as long as possible if and when they attempted to advance, preserving the strength of his own forces, and maintaining his major units intact remained the only sound bases of planning, both for current operations and at longer range. Ridgway informed General Douglas MacArthur of these tactical concepts by letter on 3 February. MacArthur agreed that occupying Seoul would yield little military gain, although he believed that seizing the city would produce decided diplomatic and psychological advantages. On the other hand, he stressed to Ridgway the military worth of nearby Kimpo Airfield and the port of Inchon, both below the Han, and urged their capture. These facilities already had become objectives of Operation Thunderbolt. To Ridgway's larger concept, of holding along the Han River-Yangp'yong-Hoengsong-Gangneung line unless enemy forces voluntarily withdrew above the 38th Parallel, MacArthur responded in terms of developing the enemy's main line of resistance. If Ridgway developed the line below the Han, he should not attempt to break through it, but if he reached the Han without serious resistance, he should continue north until he had defined the enemy line or discovered that no line existed. As a general concept, MacArthur had in mind “to push on until we reached the line where a balance of strength was achieved which was governed by the relativity of supply." Ridgway, on the other hand, was primarily interested in holding whatever line best suited his basic plan of punishing the enemy as severely as possible at the least cost to his own forces. The difference in concept was perhaps subtle but was substantial enough to prompt Ridgway to bring up the matter again when MacArthur next visited Korea.

Advance to the Han River (5-11 February)

At the resumption of the operation on 5 February, the two I Corps' assault divisions spearheaded their advance with tanks. Milburn previously had arranged but had not yet called for the strong armored thrust along the west coast ordered by Ridgway on 31 January. On Milburn's further order, two tank battalions, two infantry battalions, an artillery battalion, and a company of engineers were to assemble under Brigadier general Frank A. Allen, Jr., assistant commander of the 1st Cavalry Division. When called, Task Force Allen was to exploit any breakthrough that might occur, especially in the 25th Division's zone, and was particularly to block the lateral Inchon-Yongdungp'o road and cut off enemy forces located west of Kimpo Airfield. Between 5 and 8 February the smaller armored forces ranging ahead of the I Corps' methodical infantry advance were frequently delayed but seldom hurt by numerous minefields located on the curves and shoulders of roads and on bypasses around destroyed bridges. The mines, mostly wooden boxes with five to six pounds of explosives in each, were poorly laid and camouflaged. Most were visible, and mine detectors picked up the metallic igniters of those more deeply buried. Gains of 1–4 miles (1.6–6.4 km) through the 8th carried the 25th Division on the left within 5 miles (8.0 km) of the Inchon-Yongdungp’o road and took the forwardmost force of the 3rd Division at the right within 6 miles (9.7 km) of the Han itself. Beginning on the 6th, Milburn's forces captured troops from the KPA 47th Division in the area north and northeast of Anyang. By the 8th it appeared that all or part of the KPA 17th Division had relieved the 47th at Inchon; that the latter had joined the KPA 8th Division in holding back the I Corps, taking up positions near the center of the Corps' zone; and that the bulk of the 50th Army was sideslipping to the east.

The strongest enemy positions facing the I Corps on the 8th lay between Routes 1 and 55 across heights centered on Kwanak Mountain, due south of Seoul, where the KPA 47th Division had been identified. Since the Kwanak heights were the last defensible ground on the southern approaches to Seoul, their capture could climax the I Corps' advance to the Han. Ridgway emphasized this probability to Milburn at a meeting of Corps commanders on the 8th and urged him to push vigorously against the Kwanak defenses. Earlier, after learning of the 47th Division's entry on line, Ridgway asked Admiral C. Turner Joy to arrange an amphibious landing demonstration at Inchon to discourage further strengthening of the KPA screen and perhaps draw off some opposing forces. Joy dispatched ships from Sasebo, Japan, and from Pusan to join those already in Inchon waters for a demonstration on the 10th.

Aftermath

While the UN forces established themselves on the southern bank of the Han River, the PVA/KPA forces moved their operations further east launching the Fourth Phase Campaign, achieving initial successes at the Battle of Hoengsong but then being stopped and routed at the Battle of Chipyong-ni. On 20 February Ridgway ordered Operation Killer to eliminate the PVA/KPA forces.