When U.S. military strategists planned the invasion of Iwo Jima, they estimated victory within five days. The United States did not anticipate the Japanese strategy of under-ground bunkers and suicidal soldiers that held off American forces for over a month and caused a devastating number of casualties. Iwo Jima was a strategic outpost for both the Japanese and the Americans. It was part of Japan, and, until then, Japanese soil had not been successfully invaded in over 5,000 years. The Japanese did not want to hold on to Iwo Jima simply for pride or tradition. Japan knew that if the Americans captured the tiny island, they could mercilessly bomb Tokyo and other Japanese strongholds. Japan no longer had the men and the supplies to fight a massive war. Therefore, the strategy in Iwo Jima was more about delay than men or victory.
The Japanese strategy in Iwo Jima consisted of three parts. First, the Japanese did not fight above ground. They dug over 1,000 rooms in the rock and over 16 miles of tunnels connecting the rooms. This allowed the Japanese to have cover on an island that lacked sufficient vegetation or landmarks to hide behind. This protected the Japanese soldiers and left the American troops vulnerable. The second part of the strategy called for no Japanese survivors. The Japanese troops on Iwo Jima knew reinforcements could not be sent, and so they fought to the death. The third part of the strategy was that each Japanese soldier was ordered to kill ten Americans before they could sacrifice themselves. The Americans did not expect such a position from their enemy. This dedication by the Japanese military held off the Americans for over a month and cost 6,800 American lives. The Japanese lost almost 20,000 men in this fight to the death. The killing fields of Iwo Jima stands as a testament to the sacrifice of those who fight, no matter which side they fight for.
Sources: http://www.world-war-2.info/battle/bt_14.php; http://www.iwojima.com/battle/battlea.htm