<P> By February 19, 1945, the day the Americans invaded, 11 miles of a planned 17 miles of tunnel network had been dug . Besides the Nanpo Bunker, there were numerous command centers and barracks that were 75 feet deep . Tunnels allowed for troop movement to go undetected to various defense positions . </P> <P> 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 explosive rockets . </P> <P> Nonetheless, the Japanese supply was inadequate . Troops were supplied 60% of the standard issue of ammunition sufficient for one engagement by one division, and food and forage for four months . </P> <P> 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 . </P>

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