[90] MarCorps Board Study, v. II, app. 67.
These officers did not begin their new assignment in time to contribute to the preliminary X Corps over-all scheme of maneuver. The main provisions, as communicated to General Smith at General Ruffner’s briefing conference of 23 August, were as follows:
(1) The 1st Marine Division, as the landing force, was to seize the urban area of Inchon (line A-A); to capture a beachhead (line B-B); to advance as rapidly as possible and seize Kimpo Airfield (line C-C); to clear out the south bank of the Han River (line D-D); to cross the river, seize Seoul and secure the commanding ground to the north (E-E); and, finally, to fortify and occupy this line with reduced forces until relieved (apparently by the 3d Infantry Division, still in the United States), whereupon the Division was to recross the Han and seize a line (F-F) about 25 miles southeast of Seoul.
(2) The 7th Infantry Division was to land behind the Marines and advance on their right flank to seize the commanding ground south of Seoul and the south bank of the river (line D-D); to continue the advance to phase line (E-E); and to conduct a reconnaissance in force to the south (line F-F). There, on the line from Suwon to Kyongan-ni, the 7th Infantry Division and 1st Marine Division would form the strategic anvil as Eighth Army forces advanced from the Pusan Perimeter in the role of hammer.
(3) The 1st Marine Aircraft Wing was to furnish air support, air direction, and air warning for the Corps with units operating from Kimpo Airfield. It was also to be prepared to operate a control center ashore on order.[91]
[91] Ibid., v. I, III-B-8, and v. II, app. 16; O. P. Smith, Notes, 48–49.
The Special Plans Staff gave General Smith a study explaining the purposes of these maneuvers. “The B-B line in this study appeared to be a suitable beachhead line,” he commented, “and we decided to concentrate our efforts on plans for its seizure. Subsequent operations would be reserved for later consideration.”[92]
[92] O. P. Smith, Notes, 50.
Intelligence Planning for Inchon
Good planning, of course, depended on accurate intelligence. All possible information about the objective area had been gathered by the staff of PhibGru One before the arrival of the 1st Marine Division planners. Air Force planes had taken hundreds of photographs at every stage of the tide. Hydrographic reports and navigation charts had been studied. Army and Navy men familiar with Inchon during the American occupation after World War II were interrogated as well as NKPA prisoners captured by the Eighth Army.