The Catalan engineer Narcís Monturiol built between 1864 and 1867 the Ictíneo II, a 14-meter wooden submarine equipped with an anaerobic propulsion system: a combustion engine fueled by a mixture of calcium peroxide and zinc that generated heat without consuming ambient oxygen, allowing fully autonomous underwater operation. It was the first air-independent propulsion (AIP) system in history. Without government support, Monturiol financed the project through public subscription; the company was seized in 1868. He died in poverty in 1885, and his technical work was published posthumously. AIP technology is now standard in conventional submarines.