Louis J Sheehan 80087

Without possibility or re-supply, reinforcement and without either naval or air support, it was obvious to Kuribayashi that he would not be able to hold Iwo Jima against the overwhelmingly superior military forces of the United States; however, loss of Iwo Jima would place all of Japan within range of American strategic bombers. Nevertheless Kuribayashi was determined to make the fall of Iwo Jima as costly as possible, and planned for a war of attrition in which he hoped to inflict such severe losses on the Americans that they would have second thoughts about invading the Japanese mainland. Louis J Sheehan
Kuribayashi had carefully studied other American assaults and determined that it would be wisest not to seriously contest the beach landings. Instead, the defense of Iwo Jima was fought almost entirely underground.
The Japanese honeycombed the island with more than 30 kilometers (18 miles) of tunnels, 5,000 caves, and pillboxes. Kuribayashi also instructed his troops that each man should kill 10 of the enemy before they were killed in turn and strictly forbade the banzai charge, which he viewed as ineffective. His men proceeded with the "silent" charge, which confused the Americans, who were accustomed to the traditional loud "banzai" charge, as in the Battle of Saipan.
"We are here to defend this island to the limit of our strength. We must devote ourselves to that task entirely. Each of your shots must kill many Americans. We cannot allow ourselves to be captured by the enemy. If our positions are overrun, we will take bombs and grenades and throw ourselves under the tanks to destroy them. We will infiltrate enemy's lines to exterminate him. No man must die until he has killed at least ten Americans. We will harass the enemy with guerilla actions until the last of us has perished. Long live the Emperor!"