In July 1945, Indianapolis completed a top-secret high-speed trip to deliver uranium and other components for "Little Boy", the first nuclear weapon used in combat, to the Tinian Naval Base, and subsequently departed for the Philippines on training duty.

The remaining 890 faced exposure, dehydration, saltwater poisoning, and shark attacks while stranded in the open ocean, with few lifeboats and almost no food or water.

[a] On 19 August 2017, a search team financed by Microsoft co-founder Paul Allen located the wreckage in the Philippine Sea lying at a depth of approximately 18,000 ft (5,500 m).

[7] Ordered for the U.S. Navy in fiscal year 1930, Indianapolis was originally designated as a light cruiser because of her thin armor and given the hull classification symbol CL-35.

After overhaul at the Philadelphia Naval Shipyard, she sailed to Maine to embark President Franklin D. Roosevelt at Campobello Island, New Brunswick, on 1 July 1933.

[12] President Roosevelt underwent his crossing the line ceremony during this cruise on 26 November: an "intensive initiation lasting two days, but we have all survived and are now full-fledged Shellbacks".

Attacking from the south through the Owen Stanley mountain range, the US air forces surprised and inflicted heavy damage on Japanese warships and transports, losing few aircraft.

Through mid-1943, Indianapolis remained near the Aleutian Islands, escorting American convoys and providing shore bombardments supporting amphibious assaults.

She sortied from Pearl Harbor on 10 November, with the main body of the Southern Attack Force for Operation Galvanic, the invasion of the Gilbert Islands.

On D-Day, 15 June, Admiral Spruance heard that battleships, carriers, cruisers, and destroyers were headed south to relieve threatened garrisons in the Marianas.

Indianapolis returned to VADM Mitscher's task force in time to strike Tokyo, again on 25 February, and Hachijō, off the southern coast of Honshū, the following day.

The fast carrier force was tasked with attacking airfields in southern Japan until they were incapable of launching effective airborne opposition to the impending invasion.

When TF 54 began pre-invasion bombardment of Okinawa on 24 March, Indianapolis spent seven days pouring 8-inch shells into the beach defenses.

Tracers converged on it, causing it to swerve, but the pilot managed to release his bomb from a height of 25 ft (7.6 m), then crashing his plane into the sea near the port stern.

The bomb plummeted through the deck, into the crew's mess hall, down through the berthing compartment, and through the fuel tanks before crashing through the keel and exploding in the water underneath.

After major repairs and an overhaul, Indianapolis received orders to undertake a top-secret mission: transporting a "critical shipment" of material for the first atomic bomb to Tinian Island.

In its hold was loaded the complete non-nuclear parts for a Little Boy gun-type atomic bomb unit (L-11) and several hundred pounds of scientific instruments and tools.

[16] Indianapolis departed San Francisco's Hunters Point Naval Shipyard on 16 July 1945, within hours of the Trinity test in New Mexico.

[16] The weapon, which would be dropped on Hiroshima on the morning of 6 August, would be inscribed with numerous autographs and graffiti by ground crews who loaded it into the plane.

[21] After its stop at Tinian, Indianapolis the continued on its route to Guam, where a number of the crew who had completed their tours of duty were relieved by other sailors.

Leaving Guam on 28 July, she began sailing toward Leyte, where her crew was to receive training before continuing on to Okinawa to join Vice Admiral Jesse B. Oldendorf's Task Force 95.

[citation needed][22] At 00:15 on 30 July 1945, Indianapolis was struck on her starboard side by two Type 95 torpedoes, one in the bow and one amidships, from the Japanese submarine I-58,[19] captained by Commander Mochitsura Hashimoto, who initially thought he had spotted the New Mexico-class battleship Idaho.

Indianapolis took on a heavy list (the ship had a great deal of armament and gun-firing directors added as the war went on, and was therefore top-heavy)[24] and settled by the bow.

After nightfall, the destroyer escort USS Cecil J. Doyle, the first of seven rescue ships, used its searchlight as a beacon and instilled hope in those still in the water.

[27] Many of the survivors were injured, and all suffered from lack of food and water (leading to dehydration and hypernatremia; some found rations, such as Spam and crackers, among the debris of the Indianapolis), exposure to the elements (dehydration from the hot sun during the day and hypothermia at night, as well as severe desquamation due to continued exposure to saltwater and bunker oil), and shark attacks, while some killed themselves.

The vessel's failure to arrive on schedule was known at once to Gibson, who failed to investigate the matter and made no immediate report of the fact to his superiors.

[35] Captain Charles B. McVay III, who had commanded Indianapolis since November 1944 through several battles, survived the sinking, though he was one of the last to abandon ship, and was among those rescued days later.

Scott's effort led to an increase in national publicity,[40] which got the attention of retired Congressional lobbyist Michael Monroney, who had been scheduled to be assigned to Indianapolis before she shipped out on her final voyage.

[50] A year after the discovery of the records, the wreck was located by Paul Allen's "USS Indianapolis Project" aboard the research vessel Petrel [51] on 19 August 2017, at a depth of 18,000 ft (5,500 m).

[55] The full exposition of the method by which the wreck was located and documented was released in another PBS documentary on 8 January 2019 titled USS Indianapolis: The Final Chapter.