One of the reasons for the sudden change was the receipt of a message by the 1st Marine Division at 2120, informing that the 6th ROK Division was under heavy attack to the west of the Marines. Meanwhile, an on-the-spot questioning of a CCF prisoner just taken by the KMCs convinced the command and staff of the 1st Marine Division that the CCF 5th Phase Offensive was only hours away and gathering momentum. Thanks to this timely interpretation, all forward Marine units were alerted two hours before the main blow fell. It was on the left of the 1st Marine Division that the situation first became critical. The 6th ROK Division had never quite succeeded in closing up the gap on its right and restoring contact with the Marines. But this failure was trivial as compared to the collapse of the entire ROK division an hour before midnight, leaving a gap wide enough for a major breakthrough. The 1st Marine Division took prompt measures to cope with the emergency. As early as 2130, the 1st Marines, in reserve just north of Chunchon, were alerted to move one battalion to contain a possible enemy threat to the Division left flank. A second message an hour later called for immediate execution. And at midnight the Division Provost Marshal was directed to stop ROK stragglers and place them under guard. The Division Reconnaissance Company received orders to aid the military police.[162] [162] CG 1stMarDiv msg to CO 1stMar 2130 and 2232 22 Apr 51 in Div In&Out #12; 1stMarDiv _HD_, Apr 51, 6 and 50. Colonel Francis M. McAlister, commanding the 1st Marines, selected Lieutenant Colonel Robley E. West’s 1st Battalion to carry out Division orders. “By midnight we were all on trucks and rolling on the roads north,” wrote Second Lieutenant Joseph M. Reisler in a letter home. “Mile after mile, all the roads were covered with remnants of the ROKs who had fled. Thousands of them [were] straggling along the roads in confusion.”[163] [163] 2dLt J. M. Reisler, ltr to family of 1 May 51. Despite these preparations for trouble on the left flank, the KMCs on the right and the 5th Marines in the center were first in the Division to come under attack. During the last minutes of 22 April the 2d KMC Battalion had it hot and heavy on Hill 509. To the left the 1st KMC Battalion, partially encircled, notified the 5th Marines of a penetration. The effects were felt immediately by 1/5, with its CP in Hwachon. Hill 313 was the key to the town, being located at the Hwachon end of a long ridge forming a natural avenue of approach from the northeast. Captain James T. Cronin’s Baker Company of 1/5 had the responsibility for protecting the CP and shifting troops to the right flank if necessary. He sent Second Lieutenant Harvey W. Nolan’s platoon to run a race with the enemy for the occupation of Hill 313. Attached in excess of T/O for familiarization was Second Lieutenant Patrick T. McGahn.[164]