United Nations 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 10–20 miles (16–32 km) 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.

[1] 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.

[1]: 347 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.

Ridgway agreed with 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.

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 20 to 30 miles (32 to 48 km) 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.

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.

Following the lower shoreline of the reservoir, it then turned slightly north to a depth of 10 miles (16 km) above the parallel before falling off southeastward to the Yangyang area on the coast.

The 187th Airborne Regimental Combat Team (187th RCT), which had left the I Corps' zone for Taegu on 29 March, meanwhile was to be ready to return north to reinforce operations wherever needed.

[1]: 349 While these forces established themselves in reserve, Ridgway planned to launch Operation Dauntless, a limited advance toward the Iron Triangle by I and IX Corps.

They would create, in effect, a broad salient bulging above the Kansas Line between the Imjin River and Hwach'on Reservoir and reaching prominent heights commanding the Ch'orwon-Kumhwa base of the communications complex.

Once Ridgway's forces reached their Kansas-Wyoming objectives MacArthur intended to limit UN operations to reconnaissance and combat patrols, none larger than a battalion.

[1]: 350 Ridgway set an opening date for Operation Dauntless late on 9 April, after all but X and ROK III Corps had reached the Kansas Line.

On the east flank of the advance, the 27th British Commonwealth Brigade of IX Corps had cleared minor PVA 40th Army forces from Paegun Mountain above the headwaters of the Kap'yong River to reach the Utah Line on 16 April.

East of Route 3, the 24th Division attacking through the Kwangdok-san ridges shouldering the Yongp'yong River gained scarcely 1 mile (1.6 km) in three days.

At the left, the ROK 1st Division sat astride Route 1 with its tank destroyer battalion (still organized and fighting as an infantry unit) and 11th and 12th Regiments stretched out from the mouth of the Imjin to the river's Korangp'o-ri bend 15 miles (24 km) upstream.

ROK patrols later moved along Route 1 as far as Kaesong, the medieval capital of Korea some 12 miles (19 km) above the Imjin, without making contact.

The light contact and wide dispersion of a single regiment did suggest a screen, but as ROK and British patrols continued to probe the thin enemy positions through 20 April, no evidence appeared of PVA forces massing behind them.

[1]: 373 The most visible evidence of enemy activity appeared as Eighth Army forces closed on the Kansas and Utah Lines were billows of smoke rising at numerous points ahead of them.

Having learned that two fresh army groups (the XIX and III) were in the general Kumch'on-Koksan-Ich'on area, he believed the "greatest enemy potential" for a major attack to be from the north and northwest across the Imjin.

Incoming reports to Van Fleet from Corps' commanders and Tarkenton's own daily intelligence summaries all described enemy forces as maintaining a "defensive attitude.

"[1]: 374 Since all units were on or near their Utah and Kansas objectives, and since there was no clear sign that the impending enemy offensive would start immediately, Van Fleet elected to open the second phase of Operation Dauntless.

[1]: 374 The I Corps' final Dauntless objectives lay in the zones of the 25th and 24th Divisions stretching north of the Utah Line to Ch'orwon and Kumhwa at the base of the Iron Triangle.

In the Pogae-san heights, the 25th Division attacked toward Ch'orwon, but made no substantial progress after receiving increasing artillery fire during the day and becoming involved in hard fights right at the Utah Line, especially in the zone of the Turkish Brigade along Route 33.

Below the Iron Triangle, the resistance that began to stiffen on 19 April had been expected to grow progressively heavier as I Corps' forces moved above the Utah Line.

North and northeast of Yanggu, 2nd and 7th Division patrols, after several days of nearly fruitless searches, located several groups of 600-1000 KPA immediately above the Corps' front.

[1]: 375  The first indication that the enemy would repeat this pattern appeared during the night when I Corps' patrols reconnoitering above the Imjin ran into PVA positions that were stronger and nearer the river than those encountered during past searches.

On the east flank of the advance, the Hwacheon Dam, defended so stoutly by PVA 39th Army forces only a few days earlier, fell to the 1st Korean Marine Corps Regiment without a fight.

Immediately east, artillery pilots spotted PVA columns nearing 24th Division lines late in the afternoon and brought them under fire as they came within range.

[1]: 377 On the night of 22 April, the PVA opened their Spring Offensive pushing back the UN forces across the entire front, erasing all the gains of Operations Dauntless and Rugged.