 These warships were described to have their sides protected with iron plates.In 1578, Oda Nobunaga, the Japanese "daimyō", had made six Atakebune (大安宅船) which were called, according to one source, "Tekkōsen" (鉄甲船|鉄甲船), literally meaning "iron ships".implying that their superstructure may have been reinforced with iron plates against cannon and fire arrows.