I-401

The Sen Toku-class I-401 (伊号第四百一潜水艦) was once the largest submarine in the world. It was commanded by Lieutenant Commander Nobukiyo Nambu of the Imperial Japanese Navy during World War II. Capable of carrying three two-seat Aichi M6A1 "Seiran" (Mountain Haze) float torpedo bombers, the Sen Tokus were built to launch a surprise air strike against the Panama Canal. She calls herself Shioi. While the "shi" and "i" in her name stands for 4 and 1 in Japanese respectively, the "o" in her name is just pronounced as the letter instead of an abbreviation of the number 0. The brainchild of Admiral Isoroku Yamamoto, the Sen Toku-class submarines were built to attack major US coastal cities by deploying specialized seaplane bombers, and were designed with the ability to operate for extended periods of time without refueling, allowing them to sail anywhere in the world to reach both the US Western and Eastern seaboards. With the death of Admiral Yamamoto however, the Sen Toku-class were repurposed to attack the Panama Canal in an attempt to stem US naval reinforcements from the Atlantic as the strategic situation had deteriorated for the Japanese since their defeat at the Battle of Midway. This plan would also be abandoned after the fall of Okinawa, and the submarines were tasked with attacking the invading US fleet assembling at Ulithi Atoll. Ultimately, the war ended before the Ulithi Atoll attack could be launched, and the Sen Toku-class submarines were surrendered to the US. She was used as a target ship by the US Navy to prevent her from falling into the hands of the Soviet Union before the Cold War.