[1]: 345–6 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 north-east and Seoul in the south-west.

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.

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.

While Milburn's forces along the Imjin River stood fast, the 24th and 25th Infantry Divisions in the eastern half of the I Corps' zone attacked north on either side of Route 3 on the morning of 3 April.

Resistance to the 24th Division was desultory except at the far right where the 2nd Battalion, 21st Infantry, stalled on the western slopes of Kungmang Mountain on 4 April, under fire from a strong PVA 40th Army force dug in on the crest behind barbed wire and antipersonnel mines.

[1]: 353 Ridgway suspected that the stiff resistance to the 1st Cavalry Division was related to enemy plans to obstruct IX Corps' movement by releasing the reservoir's water through the Hwacheon Dam and flooding the Pukhan.

[1]: 353–5 As the advance got under way, the IX Corps' engineer calculated that simultaneously opening all sluice gates and penstocks when the reservoir was full would raise the Pukhan 10-foot (3.0 m) to 12-foot (3.7 m) in the vicinity of the Kansas Line and would flood much of the Chuncheon basin.

With the reservoir level well below maximum, Ridgway attached no urgency to the seizure; he adjusted the Wyoming Line to include the dam, making it an objective not of Rugged but of Operation Dauntless to follow.

[1]: 356–8 Although the reservoir was only half full, PVA troops and Korean employees of the dam power plant began opening sluice gates at midnight on the 8th.

He opened the attack with inevitably reduced fire support since the severely convoluted ground for a distance of 7 miles (11 km) below the dam prevented tank and artillery movements.

Meanwhile, to assist resupply and the displacement of the battalion's heavy weapons, Company G began to clear a segment of the regimental supply road running north along the reservoir and west through the valley at the foot of the approach ridge.

After crossing the valley road, Company F stalled under mortar, small arms, and machine gun fire from Hill 364 and from mutually supporting bunkers on heights above the Pukhan to the northwest.

battery of the 1st Marine Division's 4th Field Artillery Battalion were now within range of Harris' objectives, but worsening weather-a mix of rain, sleet, snow, and fog-eliminated air support.

[1]: 360 Harris had considered a reservoir crossing operation on the 9th, alerting the 4th Ranger Company to that possibility and setting staff members to getting twenty assault boats from the division's 8th Engineer Combat Battalion.

Attempts to retrieve equipment and transport it to the reservoir over the poor supply road produced just nine boats and four motors by the time set for the Rangers' crossing.

[1]: 360 The Ranger company commander, Captain Dorsey Anderson, embarked two platoons, artillery and mortar observers, and a machine gun section in the first lift.

Concealed by darkness and paddling the boats to maintain silence, the first-wave forces reached the eastern peninsula undetected, but were stopped by small arms and machine gun fire when they moved onto high ground above the landing point after daylight.

PVA fire striking the following waves of Rangers as they crossed the reservoir in daylight grew heavy enough to force part of the last lift to return to the south shore.

Elsewhere, the diversionary attack across the Pukhan ended when intense fire from the northwest blocked all early morning attempts by a Company A patrol to search the still-swollen river for crossing sites.

[1]: 361 Following Company I's drawn-out reservoir crossing, however, Harris realized that the shortage of boats and motors would prevent the remainder of the 3rd Battalion from reaching the peninsula before dark.

Completing the return trip after midnight, they moved on to join the remainder of the regiment, which Harris had pulled back to the Kansas Line after ordering the evacuation of the eastern peninsula.

[1]: 361 As Harris began pulling his forces off the peninsula, Hoge decided to forego any further separate action against the dam and authorized the relief of the 7th Cavalry by the 1st Korean Marine Corps Regiment on 12 April.

In any case, since Ridgway meanwhile had ordered the opening of Operation Dauntless, Hoge elected to wait until then, when the dam would be an objective of a full IX Corps' advance to the Wyoming Line.