Japanese Defensive Tactics at Iwo Jima (1945)

The Battle of Iwo Jima (Feb–Mar 1945) showcased a deeply layered Japanese defense doctrine designed to inflict maximum casualties and delay the US advance toward the home islands. Lieutenant General Tadamichi Kuribayashi abandoned beach-line defense in favor of defense in depth.

Key Tactics

1. Underground Fortress Network – 18 km of tunnels linking hundreds of bunkers, pillboxes, artillery caves, and command posts, many blasted into volcanic rock. Allowed troops to move, resupply, and counterattack unseen.
2. Kamikaze Attacks – While not launched from Iwo Jima itself (no operational airfield), land-based kamikazes from Japan and Formosa struck the US fleet offshore, sinking Bismarck Sea and damaging others.
3. Banzai Charges – Few large-scale charges; Kuribayashi forbade wasteful assaults. Instead, small-unit night infiltration and counterattacks were used.
4. Night Infiltration & Close-Quarters Combat – Japanese troops exploited darkness and terrain to infiltrate Marine lines, using grenades, satchel charges, and knives.
5. Scorched Earth / Resource Denial – As positions fell, defenders destroyed water tanks, food caches, and communications to deny them to the enemy.
6. Artillery & Mortar Fire from Concealed Positions – Pre-registered fires on landing beaches and approach routes; "spigot mortars" and 320 mm spigot mortars caused heavy casualties.

Outcome

36-day battle; ~6,800 US dead, ~19,000 wounded. Of ~21,000 Japanese defenders, only 216 surrendered; the rest fought to the death. The island provided emergency landing fields for B-29s, but the cost sparked debate over its strategic necessity.