Following the gunnery duel and an air attack of the island at 06:10, the naval bombardment of the island began in earnest and was sustained for the next three hours. Two minesweepers, with two destroyers to provide covering fire, entered the lagoon in the pre-dawn hours and cleared the shallows of mines. A guide light from one of the minesweepers then guided the landing craft into the lagoon, where they awaited the end of the bombardment. The plan was to land Marines on the north beaches, divided into three sections: Red Beach 1 on the far west of the island, Red Beach 2 in the center just west of the pier, and Red Beach 3 to the east of the pier. Green Beach was a contingency landing beach on the western shoreline and was used for the D+1 landings. Black Beaches 1 and 2 made up the southern shore of the island and were not used. The airstrip, running roughly east–west, divided the island into north and south.