From L-minus 45 to L-minus 2, the cruisers and destroyers would dump a total of 2,845 shells on Inchon and its outlying island, each ship concentrating on specifically assigned target areas. From L-minus 15 to L-minus 2, each of the three LSMRs would saturate Wolmi-do with 1,000 5-inch rockets. Most of the ships were to cease fire two minutes before the landing on GREEN Beach, when Marine planes strafed possible enemy positions for final shock effect. Four of the destroyers would continue to pound Inchon targets with 55 shells during the short air attack.
Another intricate piece in the mosaic of destruction was the mission assigned to one LSMR for the period immediately preceding and following the landing of 3/5. The lone rocket ship would lumber parallel to Wolmi-do’s shoreline, across the front of the advancing first wave, and pour 40mm shells into the beach area. Clearing the route of approach to GREEN Beach just in time for the landing craft to speed by, the LSMR was to continue southward along the coast and direct its heavy automatic fire at the slopes in advance of the attacking troops.
Once Wolmi-do was secured, the full fury of the support ships would rain down on targets in the Inchon area. From H-minus 180 to H-minus 5, the cruisers and destroyers were scheduled to blast their assigned targets with a total of 2,875 shells. Chiming in at H-minus 25 with 2,000 rockets apiece, the LSMRs would pulverize RED and BLUE Beaches until five minutes before the landings by the two Marine regiments. At that time, all ships must cease fire to clear the way for strafing Corsairs and Navy Skyraiders.
The meticulous planning left nothing to chance, even with the assumption that a foothold would be successfully established by darkness. During the night of D-day, the cruisers would expend an additional 250 shells on interdictory missions, and the destroyers were authorized to fire a total of 300 5-inch rounds on call from the infantry. To help thwart any possible enemy ambitions at dawn of D-plus 1, the cruisers would be prepared to unload 300 shells for interdiction and call fires, while the destroyers stood poised with the same number of high-explosive missiles plus 300 illuminating shells.
Other details of the elaborate plan dealt with the coordination of naval gunfire, air, artillery, mortars, and rockets. At certain times, for example, Marine and Navy gunners could fire only below a maximum trajectory of 1100 feet, so that planes, whose minimum altitude was set at 1500 feet, could pass safely over Inchon during strikes on adjacent areas. During those periods when close support Corsairs were scheduled to descend on beachhead targets, all other heavy weapons would fire completely clear of broad circles defining strike areas for the air missions.
More tables and instructions in the formidable appendixes of Admiral Doyle’s operation order assigned shore fire control parties their ships and radio frequencies, ships their battery missions and ammunition allowances, and a host of other tasks and responsibilities.
Air Support for Inchon
Air support, of course, was closely related to naval gunfire planning. After the arrival of CG 1st MAW and his staff at Tokyo on 3 September, part of the group proceeded at once to Itami Air Force Base while General Harris and selected staff members remained at Tokyo for planning conferences.
Air support planning for Inchon was based on the decision that the sky over the objective area was to be divided between the organic air units of JTF-7 and X Corps.
JTF-7 counted on its fast carrier task force, TF-77, to gain air supremacy and furnish deep support and interdiction strikes. Close support for the landing was to be provided by the two squadrons of TG-90.5, on board the CVEs Sicily and Badoeng Strait, which had been the main air components of MAG-33 in support of the 1st Marine Provisional Brigade. In addition, the Attack Force commander could also call upon the aircraft of TF-77 for close support.