Description As 1951 drew to a close, a lull had settled over the battlefield. Fighting tapered off to a routine of patrol clashes, raids, and bitter small-unit struggles for key outpost positions. The lull resulted from Ridgway's decision to halt offensive operations in Korea, because the cost of major assaults on the enemy's defenses would be more than the results could justify. Furthermore, the possibility of an armistice agreement emerging from the recently reopened talks ruled out the mounting of any large-scale offensive by either side. On 21 November Ridgway ordered the Eighth Army to cease offensive operations and begin an active defense of its front. Attacks were limited to those necessary to strengthen the main line of resistance and to establish an adequate outpost line.
In the third week of December the U.S. 45th Division, the first National Guard division to fight in Korea, replaced the 1st Cavalry Division in the I Corps sector north of Seoul. The 1st Cavalry Division returned to Japan.
In the air, U.N. bombers and fighter-bombers continued the interdiction campaign (Operation STRANGLE, which the Far East Air Forces had begun on 15 August 1951) against railroad tracks, bridges, and highway traffic. At sea, naval units of nine nations tightened their blockade around the coastline of North Korea. Carrier-based planes blasted railroads, bridges, and boxcars, and destroyers bombarded enemy gun emplacements and supply depots. On the ground, the 155-mile front remained generally quiet in the opening days of 1952. Later in January the Eighth Army opened a month-long artillery-air campaign against enemy positions, which forced the enemy to dig in deeply. During March and April Van Fleet shifted his units along the front to give the ROK Army a greater share in defending the battle line and to concentrate American fire power in the vulnerable western sector.