The final objective line of the operation, the Idaho Line, was anchored in the west on the Han River 8 miles (13 km) east of Seoul.
From that point it looped steeply northeastward through the eastern third of the I Corps' zone and almost to the 38th Parallel in the IX Corps’ central zone, then fell off gently southeastward across the X Corps and ROK zones to Hap’yong-dong, an east coast town 6 miles (9.7 km) north of Gangneung.
Since Line Idaho traced a deep salient into PVA/KPA territory, a successful advance to it would carry the Eighth Army, in particular IX Corps in the center, into an area believed to hold a large concentration of PVA/KPA forces and supplies.
Prize terrain objectives in the central zone were the towns of Hongcheon and Chuncheon.
Both were road hubs, and Chuncheon, nearer the 38th Parallel, appeared to be an important PVA/KPA supply center.
In the major Ripper effort, IX Corps, now commanded by Major General William M. Hoge, was to seize the two towns as it moved some 30 miles (48 km) north to the deepest point of the Idaho salient.
The 187th Airborne Regimental Combat Team (187th RCT), currently undergoing refresher training at Daegu, was to assist IX Corps attack should an opportunity arise to employ airborne tactics profitably.

To General Hoge's right, X Corps was to move to a segment of the Idaho Line whose most northerly point lay about 20 miles (32 km) above the present Corps' front.
In clearing PVA/KPA forces from this territory, General Almond was to pay particular attention to the two principal north-south corridors in his zone, one traced by the Soksa-ri-Pangnim-ni segment of Route 20 at the Corps' right, the other by a lesser road running south out of P’ungam-ni in the left third of the Corps' zone.
Responsibility for the remaining ground to the east was once again divided between ROK III and ROK I Corps.
Believing that the ROK sector needed to be strengthened, particularly after the Capital Division lost almost a thousand men in the ambush at Soksa-ri on 3 March, General Ridgway had detached the ROK I Corps headquarters and the ROK 3rd Infantry Division from X Corps, sending the division to rejoin ROK III Corps and reestablishing ROK I Corps with the ROK 9th and Capital Divisions in the coastal zone.
The ROK 5th Infantry Division, having reorganized after being hurt in the mid-February offensive, meanwhile rejoined X Corps.
During the Ripper advance the two ROK Corps were to secure Route 20.
In the coastal area, ROK I Corps forces already were well above this lateral road-in fact, were already on or above the Idaho Line.
Inland, ROK III Corps would have to move about 10 miles (16 km) north through the higher Taebaek ridges to get onto the Idaho Line some 5 miles (8.0 km) above Route 20.

In the I Corps' zone at the west end of the army front, General Frank W. Milburn was to retain two divisions, the ROK 1st and US 3rd, in his western and central positions along the lower bank of the Han to secure the army flank and protect Inchon, where five hundred to six hundred tons of supplies were being unloaded daily thanks to Task Force 90 and the 2nd Engineer Special Brigade.
East of Seoul on the Corps' right, the US 25th Infantry Division, now commanded by Brig.
Gen. Joseph S. Bradley, was to attack across the Han on both sides of its confluence with the southward flowing Pukhan River.
Above the Han, General Bradley's division was to clear the high ground bordering the Pukhan to protect the left flank of IX Corps and to threaten envelopment of PVA/KPA forces defending Seoul.
The final objective line of the operation, the Idaho Line, was anchored in the west on the Han River 8 miles (13 km) east of Seoul. From that point it looped steeply northeastward through the eastern third of the I Corps' zone and almost to the 38th Parallel in the IX Corps’ central zone, then fell off gently southeastward across the X Corps and ROK zones to Hap’yong-dong, an east coast town 6 miles (9.7 km) north of Gangneung. Since Line Idaho traced a deep salient into PVA/KPA territory, a successful advance to it would carry the Eighth Army, in particular IX Corps in the center, into an area believed to hold a large concentration of PVA/KPA forces and supplies. Prize terrain objectives in the central zone were the towns of Hongcheon and Chuncheon. Both were road hubs, and Chuncheon, nearer the 38th Parallel, appeared to be an important PVA/KPA supply center. In the major Ripper effort, IX Corps, now commanded by Major General William M. Hoge, was to seize the two towns as it moved some 30 miles (48 km) north to the deepest point of the Idaho salient. The 187th Airborne Regimental Combat Team (187th RCT), currently undergoing refresher training at Daegu, was to assist IX Corps attack should an opportunity arise to employ airborne tactics profitably.
To General Hoge's right, X Corps was to move to a segment of the Idaho Line whose most northerly point lay about 20 miles (32 km) above the present Corps' front. In clearing PVA/KPA forces from this territory, General Almond was to pay particular attention to the two principal north-south corridors in his zone, one traced by the Soksa-ri-Pangnim-ni segment of Route 20 at the Corps' right, the other by a lesser road running south out of P’ungam-ni in the left third of the Corps' zone. Responsibility for the remaining ground to the east was once again divided between ROK III and ROK I Corps. Believing that the ROK sector needed to be strengthened, particularly after the Capital Division lost almost a thousand men in the ambush at Soksa-ri on 3 March, General Ridgway had detached the ROK I Corps headquarters and the ROK 3rd Infantry Division from X Corps, sending the division to rejoin ROK III Corps and reestablishing ROK I Corps with the ROK 9th and Capital Divisions in the coastal zone. The ROK 5th Infantry Division, having reorganized after being hurt in the mid-February offensive, meanwhile rejoined X Corps. During the Ripper advance the two ROK Corps were to secure Route 20. In the coastal area, ROK I Corps forces already were well above this lateral road-in fact, were already on or above the Idaho Line. Inland, ROK III Corps would have to move about 10 miles (16 km) north through the higher Taebaek ridges to get onto the Idaho Line some 5 miles (8.0 km) above Route 20.
In the I Corps' zone at the west end of the army front, General Frank W. Milburn was to retain two divisions, the ROK 1st and US 3rd, in his western and central positions along the lower bank of the Han to secure the army flank and protect Inchon, where five hundred to six hundred tons of supplies were being unloaded daily thanks to Task Force 90 and the 2nd Engineer Special Brigade. East of Seoul on the Corps' right, the US 25th Infantry Division, now commanded by Brig. Gen. Joseph S. Bradley, was to attack across the Han on both sides of its confluence with the southward flowing Pukhan River. Above the Han, General Bradley's division was to clear the high ground bordering the Pukhan to protect the left flank of IX Corps and to threaten envelopment of PVA/KPA forces defending Seoul.
Operation Ripper