The mission of the 5th Marines (less 3/5 on Wolmi-do) was to seize the O-A Line, a 3,000-yard arc encompassing Cemetery Hill on the left (north), Observatory Hill in the center, and thence extending the last 1,000 yards through a maze of buildings and streets to terminate at the inner tidal basin. Each battalion would land in a column of companies, Lieutenant Colonel George R. Newton’s 1st, on the left, seizing Cemetery Hill and the northern half of Observatory Hill; while Lieutenant Colonel Harold S. Roise’s 2d secured the remainder of the latter, the hill of the British Consulate, and the inner tidal basin.[129] [129] 1st MarDiv _SAR_, Annex Queen Queen. Landing nearly three miles southeast of the 5th Marines, the 1st Regiment would seize BLUE Beach, a north-south strip fronting a suburban industrial area. BLUE Beach One, on the left, was 500 yards wide, flanked on the north by the rock revetment of a salt evaporator that jutted into the water at a sharp angle to the shoreline. A wide drainage ditch, about which little was known besides the fact that it existed, formed the south boundary. Just inland a dirt road--the sole exit from the beach--skirted the north end of a steep knoll that ran the whole width of the landing site. There being no revetment at the waterline, Marine planners hoped that amphibian tractors could crawl ashore with the assault troops.[130] [130] _Ibid._, Annex Peter Peter. [Illustration: PLAN FOR INCHON ASSAULT] BLUE Beach Two, connected to One by the drainage ditch, also extended 500 yards. Like RED Beach it was fronted by a rock sea wall. On the right half, the wall retained one side of a narrow ramp that jutted southward like a long index finger. Behind the ramp lay a cove, its shoreline at a right angle to the sea wall. During the assault, Marines would scale the waterfront of BLUE Two from LVTs, while the cove around the corner on the right, unofficially dubbed “BLUE Beach Three,” was investigated as a possible supplementary landing site.[131] [131] _Ibid._; and Col T. L. Ridge ltr to authors, 11 May 55. Preceded by a wave of LVT(A)s of Company A (Reinf), 56th Amphibian Tractor Battalion, USA, the 2d and 3d Battalions, 1st Marines, would land abreast on BLUE One and Two respectively. With two companies initially in the assault, each of the infantry battalions was to drive forward and secure its portion of the O-1 Line. This four-mile arc bent inland as far as 3,000 yards to include four main objectives, assigned as follows: 2d Battalion (BLUE One) ABLE A critical road junction about 1,000 yards northeast of the beach. DOG Hill 117, 3,000 yards northeast of the beach, commanding Inchon’s back door and the highway leading to Seoul, 22 miles away. 3d Battalion (BLUE Two)