The I-403 was a Japanese submarine that served during World War II. Launched in 1944, it was part of the Imperial Japanese Navy and designed for long-range missions. The submarine was equipped with advanced technology for its time, including torpedoes and a deck gun, allowing it to engage enemy vessels effectively. The I-403 was notable for its role in the Submarine Campaign in the Pacific Theater. However, it was ultimately sunk in 1945, marking the end of its operational history. The submarine's design and capabilities reflect the strategic importance of submarines in naval warfare during the conflict.