On December 7, 1941, after the Imperial Japanese Navy attacked Pearl Harbor and Oahu, the U.S. Army declared martial law throughout Hawaii, and it used Kahoʻolawe as a place to train American soldiers and Marines headed west to engage in the War in the Pacific. The use of Kahoʻolawe as a bombing range was believed to be critical, since the United States was executing a new type of war in the Pacific Islands. Their success depended on accurate naval gunfire support that suppressed or destroyed enemy positions as U.S. Marines and soldiers struggled to get ashore. Thousands of soldiers, sailors, Marines, airmen, and coastguardsmen prepared on Kahoʻolawe for the brutal and costly assaults on islands such as the Gilbert and Marshall Islands, the Marianas and Pelileu, New Guinea, et cetera, in the Western Pacific.