During world war ii, why did japan strongly and passionately defend iwo jima?

Iwo Jima was fiercely defended by Imperial Japan since it was considered that if Iwo Jima felt, Japan would do as well.

The order from the high commands of Japan was to defend the homeland at all costs. No one was expected to surrender. The island was a key point where Tadamichi Kuribayashi was the general in charge of resisting. He gave the order to die rather than surrender as the Samurai traditions taught.

The Japanese were practically erased from that island when a bigger American army entered. The resistance was prevented as many bunkers in the small island continued to hide soldiers.

Although this battle was highly criticized, Japan knew that they needed to gain time for organizing the regrouping of inland Japan and the ultimate defense of the nation. The raising of the American flag would strongly dishonor and morally discourage the Japanese. The raising of the flag constituted a strong message to the world as a sign of US victory.