While operations were proceeding in the Kerama Islands, Task Force 52, under the command of Admiral Blandy, supervised the specialized tasks that were an essential prelude to the invasion of Okinawa itself-the mine sweeping, underwater demolition work, and heavy, sustained bombardment of the target by ships and aircraft. Task Force 58 stood off to the north and east of Okinawa, ready to intercept any Japanese surface force approaching from the east, while Task Force 52 guarded against enemy attack from the west and against any "express runs" from the north either to reinforce or to evacuate Okinawa. During the day the ships bombarding Okinawa stayed close enough together to be able to concentrate for surface action without undue delay. At night 80 percent of Task Force 52 deployed to the northwest of Okinawa and 20 percent to the northeast. The northwest group was considered strong enough to cope with any surface force which the Japanese could bring against it; the northeast element was to deal with "express runs," and could count on the support of Task Force 58 if the enemy dispatched a larger, slower, and more easily detected force to the area east of Okinawa. In case of emergency, one force could join the other by passing through the unswept waters north of Okinawa.{109}
Bombardment of Okinawa began on 25 March when ships of the Amphibious Support Force shelled the southeast coast. The fire was executed only at long range, however, for mine-sweeping operations which had commenced the previous day were still proceeding well offshore. During the following days, as the mine sweepers cleared areas progressively nearer the coast of Okinawa, the bombardment ships were able to close in for heavier and more accurate fire. The Japanese had planted a mine field of considerable strength along the approaches to the Hagushi beaches, and until mine-sweeping operations were completed the American ships could not bring the beaches within range. Not until the evening of 29 March were the approaches to Hagushi and other extensive areas cleared in what Admiral Blandy called "probably the largest assault sweep operation ever executed." Operating under intermittent air attack, American mine sweepers cleared about 3,000 square miles in 75 sweeps.
SOFTENING UP THE TARGET was the task of the allied fleet. It stood off Okinawa to place accurate fire on known Japanese installations and to support underwater demolitions teams clearing the beaches. At the same time the fleet's air arm conducted aerial bombardment. This low-level bombing attack on L minus (below) hit enemy shipping in the mouth of the Bishi River.