JOINT BASE PEARL HARBOR-HICKAM, Hawaii (AP) — The military and a private organization have brought home the remains of 36 Marines killed in one of World War II’s bloodiest battles.

A group called History Flight recovered the remains from the remote Pacific atoll of Tarawa, the U.S. Marine Corps said. A ceremony was held Sunday in Pearl Harbor to mark their return.

History Flight has started identifying the remains, and the Defense POW/MIA Accounting Agency will complete the effort, the Marines said. The Marines plan to return the remains to their families after they’ve been identified.

More than 990 U.S. Marines and 30 sailors died during the three-day Battle of Tarawa in 1943. Japanese machine gun fire killed scores of Marines when their boats got stuck on the reef at low tide during the U.S. amphibious assault. Americans who made it to the beach faced brutal hand-to-hand combat.

Only 17 of the 3,500 Japanese troops survived. Of 1,200 Korean slave laborers on the island, just 129 lived.

The U.S. quickly buried the thousands of dead on the tiny atoll. But the graves were soon disturbed as the Navy urgently built a landing strip to prepare for an attack on the next Pacific island on their path to Tokyo.

About 520 U.S. servicemen are still unaccounted for from the battle.

Preliminary work conducted by History Flight indicates the remains of 1st Lt. Alexander J. Bonnyman, Jr., a Marine who was posthumously awarded the Medal of Honor, are among the 36 brought to Hawaii.

Gen. Joseph Dunford, the commandant of the Marines Corps, said in a statement he’s pleased to learn of the discovery of the remains at Tarawa, the site of one of the service’s most significant battles.

“It was also the first contested landing against a heavily fortified enemy, and a turning point in the development in our amphibious capability. The lessons learned at Tarawa paved the way for our success in the Pacific campaign and eventual end to the war,” Dunford said.

History Flight brought attention to the Tarawa missing when its research indicated it had found the graves of 139 U.S. servicemen. The Marathon, Florida-based organization used ground-penetrating radar, reviewed thousands of military documents and interviewed veterans to narrow down possible grave sites.