Operation Dauntless was a military operation performed by the United Nations Command (UN) during the Korean War designed to advance the UN lines to positions north of the 38th Parallel designated the Wyoming Line which would threaten the Chinese and North Korean logistics hub marked out by the towns of Pyonggang, Ch'orwon and Gimhwa-eup named the Iron Triangle. The operation immediately succeeded Operation Rugged which took the UN forces to the Kansas Line north of the 38th Parallel. The operation was initially successful, reaching its initial objectives, but was brought to a halt by the Chinese Spring Offensive on 22 April 1951.
Background
On 22 March, following the successful conclusion of Operation Courageous, US Eighth Army commander Lieutenant General Matthew Ridgway notified UN forces commander General Douglas MacArthur that he was developing plans for an advance that would take Eighth Army forces above the 38th Parallel to a general line following the upstream trace of the Ryesong River as far as Sibyon-ni () in the west, falling off gently southeastward to the Hwach'on Reservoir, then running east to the coast. As in past and current operations, the objective would be the destruction of enemy troops and materiel. MacArthur approved Ridgway's concept but also scheduled a visit to Korea for 24 March, when he would have an opportunity to discuss the plans in more detail.
Upon his return to Tokyo late on 24 March, following his conference with Ridgway and a visit to the front, MacArthur announced that he had directed the Eighth Army to cross the 38th Parallel "if and when its security makes it tactically advisable. More specifically MacArthur had approved Ridgway's concept of a general advance as deep as into North Korea.
On 27 March, Ridgway assembled Corps and Division commanders at his Yeoju headquarters and advised them that ceasefire negotiations and future US Government decisions might compel the Eighth Army to adopt a static defense. Because of its inherent rigidity, such a stance would require strong leadership and imaginative tactical thinking, he warned, to stand off a numerically stronger enemy that might not be similarly inhibited in the choice of tactics. The Eighth Army meanwhile would continue to move forward and in the next advance would cross the 38th Parallel. Ridgway agreed with General MacArthur's earlier prediction that a stalemate ultimately would develop on the battlefront, but just how far the Eighth Army would drive into North Korea before this occurred, could not be accurately assessed at that time.
Ridgway had revised his concept for advancing above the parallel since meeting with MacArthur on March 24. He planned to point his main attack toward the centrally located road and rail complex marked out by the towns of Pyonggang in the north and Ch'orwon and Gimhwa-eup in the south. This complex, eventually named the Iron Triangle, lay above the 38th Parallel in the diagonal corridor dividing the Taebaek Mountains into northern and southern ranges and containing the major road and rail links between the port of Wonsan in the northeast and Seoul in the southwest. Other routes emanating from the triangle of towns connected with Pyongyang to the northwest and with the western and eastern halves of the present front. A unique center of communications, the complex was of obvious importance to the ability of the enemy high command to move troops and supplies within the forward areas and to coordinate operations laterally.
The first phase of this advance was to occupy ground that could serve as a base both for continuing the advance toward the complex and, in view of the enemy's evident offensive preparations, for developing a defensive position. The base selected, the Kansas Line, followed the lower bank of the Imjin River in the west. From the Imjin eastward as far as the Hwach'on Reservoir the line lay to above the 38th Parallel across the approaches to the Iron Triangle. Following the lower shoreline of the reservoir, it then turned slightly north to a depth of above the parallel before falling off southeastward to the Yangyang area on the coast. In the advance to the Kansas Line, designated Operation Rugged, US I and IX Corps were to seize the segment of the line between the Imjin and the western edge of the Hwach'on Reservoir. To the east, US X Corps was to occupy the portion tracing the reservoir shore and reaching Route 24 in the Soyang River valley, and the Republic of Korea Army (ROK) III and I Corps were to take the section between Route 24 and Yangyang.