The Navy did not learn of the sinking for four days. With its delivery completed, the Indianapolis was heading toward the Philippines on July 30 when a Japanese submarine torpedoed the 600-foot-long ship, which sank in roughly 12 minutes with 300 men still aboard. The B-29 bomber Enola Gay dropped the bomb, dubbed Little Boy, on Hiroshima, Japan, on Aug.

The Indianapolis and its crew of 1,195 delivered to the island of Tinian key components for what would be the first atomic bomb used in warfare. “Due to administrative errors, many Sailors who were recovered from the ocean and buried at sea from responding vessels were misclassified as ‘missing in action’ or ‘unaccounted for,” the Navy said. The change comes after extensive research by the Naval History and Heritage Command, Navy Casualty Office, the USS Indianapolis Survivors Association, the USS Indianapolis Legacy Organization, and the Chief Rick Stone and Family Charitable Foundation, the Navy said in a news release Thursday. On Thursday, the Navy Casualty Office officially changed the status of 13 sailors who died as a result of the attack from “unaccounted for” to “buried at sea.”