Through the next 80 years, the landscape changed dramatically, with drought and uncontrolled overgrazing denuding much of the island. Strong trade winds blew away most of the topsoil, leaving behind red hardpan dirt. From 1910 to 1918, the Territory of Hawaii designated Kahoʻolawe as a forest reserve in the hope of restoring the island through a revegetation and livestock removal program. This program failed, and leases again became available. In 1918, the rancher Angus MacPhee of Wyoming, with the help of the landowner Harry Baldwin of Maui, leased the island for 21 years, intending to build a cattle ranch there. By 1932, the ranching operation was enjoying moderate success. After heavy rains, native grasses and flowering plants would sprout, but droughts always returned. In 1941, MacPhee subletted part of the island to the U.S. Army. Later that year, because of continuing drought, MacPhee removed his cattle from the island. 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. Military and naval training on Kahoʻolawe continued following World War II. During the Korean War, warplanes from aircraft carriers played a critical role in attacking enemy airfields, convoys, and troop staging areas. Mock-ups of airfields, military camps, and vehicles were constructed on Kahoʻolawe, and while pilots were preparing for war at Barbers Point Naval Air Station on Oʻahu, they practiced spotting and hitting the mock-ups at Kahoʻolawe. Similar training took place throughout the Cold War and during the War in Vietnam, with mock-ups of aircraft, radar installations, gun mounts, and surface-to-air missile sites being placed across this island for pilots and bombardiers to use in their training.