I-64 was a KD4 sub-class cruiser submarine, laid down on 28 March 1927 at the Kure Naval Arsenal and launched on 5 October 1929. Commissioned into the Imperial Japanese Navy on 30 August 1930, she joined Submarine Division 29 alongside her sister boat I-62. For nearly a decade she trained, patrolled, and drilled in the waters around Japan and China -- the kind of peacetime routine that builds competence without testing it. By November 1939 she was placed in reserve at Sasebo, her hull aging and her usefulness uncertain. Then the world changed. Recommissioned in November 1940 as Japan prepared for war, I-64 was assigned to Submarine Squadron 5 in the Combined Fleet. On 26 November 1941, twelve days before Pearl Harbor, she departed Sasebo bound for Palau. En route, her squadron was diverted to Samah on Hainan Island. The war she had been built for was finally about to begin.

I-64's second war patrol, beginning in January 1942 from Cam Ranh Bay, revealed the submarine at her most lethal. Operating from the newly captured base at Penang, she ranged across the Indian Ocean hunting Allied merchant shipping. On 22 January, west of Sibolga, Sumatra, she fired two torpedoes at the Dutch merchant ship Van Overstraten -- both missed. So I-64 surfaced, opened fire with her deck gun, and finished the job with a third torpedo after the crew abandoned ship. Four crewmen died; 113 survived.

The pattern repeated across the Bay of Bengal through late January. She shelled the British paddle steamer Idar near Ceylon, torpedoed the American cargo ship Florence Luckenbach southeast of Madras -- her crew of thirty-eight escaping in a single lifeboat -- then sank the British-Indian steamers Jalatarang and Jalapalaka on consecutive days. Thirty-eight sailors perished on the Jalatarang alone, with only eleven rescued. Thirteen more died on the Jalapalaka. By the time I-64 returned to Penang on 5 February, she had left a trail of sunken ships and grieving families stretching from Sumatra to India.

Her third patrol, launched from Penang on 6 March 1942, took her back to familiar hunting grounds off India's Coromandel Coast. While she was at sea, Submarine Division 29 was disbanded and I-64 was reassigned to Division 30 -- an administrative reshuffling that made no difference to the crew or their mission. Northeast of Madras, she surfaced and engaged the Norwegian armed cargo steamer Mabella with her deck gun, scoring twelve hits and killing six crew members before the survivors took to lifeboats. I-64 then finished Mabella with a torpedo. It was a methodical, almost procedural destruction: surface, shell, wait for the lifeboats to clear, torpedo the hulk. By 27 March she was back in Penang. Across three war patrols, I-64 had sunk at least five merchant vessels and damaged others, disrupting the Allied supply lines that connected India, Burma, and Southeast Asia.

In April 1942, I-64 sailed from Penang to Sasebo for refit. On 16 May she departed again, heading for Kwajalein to support Operation MI -- the planned invasion of Midway Atoll that would become one of the Pacific War's decisive turning points. She never arrived. At 18:03 on 17 May, USS Triton's lookouts spotted I-64 running on the surface in the open Pacific. Fourteen minutes later, Triton fired her last forward torpedo from 6,200 yards. The hit was catastrophic. Parts of I-64 were hurled a hundred feet skyward, and the submarine slipped beneath the waves stern-first in just two minutes. Triton's crew counted forty-two secondary explosions rumbling up from the depths. At 18:45, Triton's commanding officer observed roughly thirty Japanese sailors clinging to wreckage. In the vast emptiness of the Pacific, with the war raging around them, no rescue came. All eighty-one members of I-64's crew perished.

Three days after I-64 sank, the Imperial Japanese Navy -- unaware of her fate -- officially renumbered her I-164 as part of a fleet-wide reorganization. For eight days, the navy carried a ghost on its rolls, issuing orders to a submarine that existed only as scattered debris on the ocean floor. On 25 May 1942, headquarters declared her presumed missing south of Shikoku with all hands lost. She was stricken from the navy list on 10 July 1942. Today, somewhere in the deep Pacific roughly 250 miles off the southern coast of Shikoku, I-64 rests with her crew -- a time capsule of a war that was, at the moment of her sinking, still very much in its opening chapters. The Battle of Midway, the operation she was sailing to support, would begin just three weeks later and change the course of the Pacific War entirely.