The American fleet started shelling Tinian Island’s defences on 16 July, but sustained serious losses at the hands of the Japanese 50th Infantry Division, commanded by Colonel Kiyochi Ogata. The landings by the US 2nd and 4th Marine Divisions, begun on 24 July, were more successful. A decoy assault on Tinian town diverted the Japanese, while the main American force drove down the island from the north, by 30 July capturing Tinian town and airfield. The Japanese were hemmed in at the south and skirmishes continued, but the island was largely secured by 1 August. Tinian became a forward base for further Allied operations in the Pacific and a huge new airport built by the Americans at North Field became the main base from which the US went on to mount its devastating incendiary and atomic bombing raids on the cities of mainland Japan, forcing the country’s surrender on 15 August 1945.