While the Marines sat in their holes and cursed the frigid night, the quiet hills around them came alive with thousands of Red Chinese on the march. Unseen and unheard, the endless columns of quilted green wound through valleys and over mountain trails leading toward the southern tips of North and Northwest Ridges. These were the assault battalions of the 79th and 89th CCF Divisions. With seven other divisions they comprised Red China’s 9th Army Group led by Sung Shin-lun, one of the best field commanders in the CCF. Lin Pao, commanding the 3d Field Army, had dispatched Sung’s army group to northeast Korea specifically to destroy the 1st Marine Division. The knockout blow, aimed at the northwest arc of the Yudam-ni perimeter, amounted to a massive frontal assault. Another CCF division, the 59th, had completed a wide envelopment to the south, driving in toward South Ridge and Toktong Pass to cut the MSR between Hagaru and Yudam-ni.[388] [388] 1stMarDiv _SAR_, 31–32; G-2 _SAR_, 15, 30–31; _CCF Army Histories_, 13, 21. [Illustration: THE BATTLE OF NORTHWEST RIDGE MAP-14 ] This was the main effort of the CCF in northeast Korea: three divisions against two regiments of Marines. And in addition to the advantage of mass, the Reds held the trump cards of mobility and surprise. They enjoyed superior mobility because they were unencumbered by heavy weapons and hence could use primitive routes of approach in the darkness. They had the advantage of surprise because their practice of marching by night and hiding by day had concealed their approach to a large degree from UN air observation. To offset these odds, the outnumbered Marines would have to rely on superior firepower, command of the air, and another weapon called _esprit_. By 2100, Northwest Ridge was crawling with Chinese only a few hundred yards from the positions of Companies E and F, 5th Marines, and Company H, 7th Marines. The enemy troops, padding silently in their rubber sneakers, had as yet given no hint of their presence. To divert attention, the Red commander sent a patrol against 2/5’s roadblock on the MSR between Northwest and Southwest Ridges. Troops of Company D, 5th Marines, exchanged grenades with the Chinese and killed two of them. The remainder they quickly dispersed with mortar fire.