On April 16, the 77th division combined both phases of Operation ICEBERG, the name for the American plan to take Okinawa. The American forces underestimated the size of the Japanese defense, which was nearly 2,000 combatants. In addition, over 5,000 civilians joined in the defense with weapons as primitive as wooden spears.
On the morning of April 16, pre-landing bombardment commenced with 2 battleships, 4 cruisers, and 7 destroyers, pummeling the beaches while American planes assisted with bombs, rockets, and napalm. By dusk, the airfields were in American hands. Although the airfields themselves were in American hands, the territory behind them became the scene of fierce fighting by Japanese armed with grenades, determined to either kill Americans or blow themselves up, taking the enemy with them. This was the early version of a suicide bomber or a land kamikaze. This type of defensive warfare and land mines were classic to the Japanese pacific islanders and proved very effective.
The American troops adjusted their offensive plan to move in from the north attacking the town of Ie and move west toward Bloody Ridge, the key to Pinnacles southern defenses. The 2nd Battalion of the 307th repelled a vicious attack suffering heavy casualties but remained determined to hold its position on Government House Hill. Relief came when the 3rd battalion of the 307th arrived. The capture of Government House Hill enabled American troops additional possible assault positions against the Pinnacle.
By April 22, all that remained to complete the all-out victory on Pinnacle were armed civilians fighting from caves. Heavy losses were suffered by the Japanese, with 4,706 troops and 1,500 civilians losing their lives. The 77th division suffered 172 dead and 902 wounded, a costly loss of human life but a valuable base had been overtaken and secured.