By June 1944, Lieutenant General Tadamichi Kuribayashi was assigned to command the defense of Iwo Jima. Kuribayashi knew that Japan could not win the battle, but he hoped to inflict massive casualties on the American forces, so that the United States and its Australian and British allies would reconsider carrying out the invasion of Japan Home Islands.
While drawing inspiration from the defense in the Battle of Peleliu, Kuribayashi designed a defense that broke with Japanese military doctrine. Rather than establishing his defenses on the beach to face the landings directly, he created strong, mutually supporting defenses in depth using static and heavy weapons such as heavy machine guns and artillery. Takeichi Nishi’s armored tankswere to be used as camouflaged artillery positions. Because the tunnel linking the mountain to the main forces was never completed, Kuribayashi organized the southern area of the island in and around Mount Suribachi as a semi-independent sector, with his main defensive zone built up in the north. The expected American naval and air bombardment further prompted the creation of an extensive system of tunnels that connected the prepared positions, so that a pillbox that had been cleared could be reoccupied. This network of bunkers and pillboxes favored the defense. Hundreds of hidden artillery and mortar positions along with land mines were placed all over the island. Among the Japanese weapons were 320 mm spigot mortars and a variety of explosiverockets.
Nonetheless, the Japanese supply was inadequate. Troops were supplied a 60% of the standard issue of ammunitions sufficient for one engagement by one division, and food and forage enough for four months.
Numerous Japanese snipers and camouflaged machine gun positions were also set up. Kuribayashi specially engineered the defenses so that every part of Iwo Jima was subject to Japanese defensive fire. He also received a handful of kamikaze pilots to use against the enemy fleet. Three hundred and eighteen American sailors were killed by kamikaze attacks during the battle. However, against his wishes, Kuribayashi’s superiors on Honshu ordered him to erect some beach defenses. These were the only parts of the defenses that were destroyed during the pre-landing bombardment.