Two airfields served the locale in 1950. One of these, situated on the coast about five miles north of the seaport, was of minor importance. The other, known as Wonsan Airfield, on Kalma Peninsula across the harbor, ranked high as a military prize. Spacious and accessible, it was an excellent base from which to project air coverage over all of Korea and the Sea of Japan. The Japanese first developed the field as an air adjunct to the naval base at Wonsan; but after World War II, a North Korean aviation unit moved in and used it until July 1950. Thereafter, with the skies dominated by the UN air arm, Wonsan Airfield temporarily lost all military significance. Its vacant runways, barracks, and dispersal areas were given only passing attention in the UN strategic bombing pattern, although the nearby industrial complex was demolished. In addition to being situated on an excellent harbor, Wonsan is the eastern terminus of the Seoul-Wonsan corridor, the best of the few natural routes across the mountainous nation. This 115-mile road and rail passageway, once considered as a possible overland approach for X Corps, separates the northern and southern divisions of the Taebaek range, which rises precipitously from Korea’s east coast to heights of 5000 feet. Railroads and highways, primitive by western standards, also trace the seaward base of the Taebaek Mountains to connect Wonsan with Hamhung in the north and Pusan far to the south. Still another road and railway leads to Pyongyang, 100 miles across the narrow neck of the peninsula in the western piedmont. The climate along Korea’s northeast coast is comparable to that of the lower Great Lakes region in the United States. Mean summer temperatures range between 80 and 88 degrees, although highs of 103 degrees have been recorded. Winter readings drop as low as -7 degrees, but the season is usually temperate with winds of low velocity. Despite light snowfalls and moderate icing, the period from October through March is best suited to military operations, for the heavy rains of spring and summer create difficulties on the gravel-topped roads. Although members of Admiral Doyle’s Amphibious Group One (PhibGruOne) staff met with planners of the 1st Marine Division at Inchon early in October, it soon became apparent that the projected D-Day of 15 October could not be realized. Maps and intelligence data necessary for planning did not reach the Attack Force-Landing Force team until 6 October. The relief of X Corps by EUSAK was completed, not on 3 October as General Almond had anticipated, but on the 7th. Moreover, the first transport vessels to reach Inchon ran behind schedule, and they had not been pre-loaded with a ten-day level of Class I, II, and V supplies, as was promised. Planning and outloading consequently started late and from scratch, with the result that D-Day “... was moved progressively back to a tentative date of 20 October.”[43]