Japan undertook major naval building efforts in the mid to late 16th century, during the Sengoku period, when feudal rulers vying for supremacy built vast coastal navies of several hundreds of ships. The largest (and generally most dangerous) of these ships were called Atakebune.
Around that time, the Japanese daimyō Oda Nobunaga had made, according to the diary of the Abbot of the Tamon-I, six iron-covered big Atakebunes in 1578. These ships were called "Tekkōsen" (鉄甲船), literally meaning "iron ships", which is not to imply they were of iron, but that their superstructure may have been reinforced with iron plates against cannon and fire arrows. No iron-covering at all, however, was mentioned in the account of the Jesuit missionary Luís Fróis, who had also seen and described the ships. Abbot of the Tamon-I did not witness the ships actually, so the existence of the iron plates is questioned.
However, in the letter from João Rodrigues to Luís Fróis in 1593, full iron-covered Atakebune build by Toyotomi Hideyoshi was mentioned. Hideyoshi made those ships to invade Korea and their superstructure was fully covered by iron plates.
Kanpaku(Hideyoshi) commanded them to build several huge ships.Their structure above the surface is fully covered by iron, and there is tower on the deck. Bridges are covered by iron, and no wood is exposed. And whole parts are gilded very beautifully. These were worth admiring, I sometimes entered in the ships. I measured the length of one there, it was 19 jou(36.3 meter) long. These ships astonished several Portuguese who looked inside. However, these ships were frangible due to defective ribs. So some of them cleaved and sank.
The Atakebune were armed with a few cannons and numerous large-caliber arquebuses. Oda defeated Mori's navy with them at the mouth of the Kizu River, Osaka in 1578 in a successful naval blockade. These ships, the best of the Atakebune, were used somewhat in contrast to Japanese naval tactics of the time, which viewed naval combat as a battle between the crews of ships, rather than between the ships themselves (which contributed to the primary Japanese naval tactic of drawing near and boarding opposing ships, as the Japanese crews excelled at hand-to-hand combat).
These vessels may be regarded as floating fortresses rather than true warships, and were only used in coastal actions. They used oars for propulsion, as their full iron cladding, if it existed, as well as their bulk (i.e. the armament and people they were carrying) likely impeded wind-based propulsion via sails.
In the Japanese invasion of Korea the shortcomings of these ships became pronounced as they proved to be of no match to the superior build and fire power of the Korean navy's Panokseon ships, which could accommodate far more number of cannons due to sturdier structure and thus were employed in a distance engagement by cannon tactics rather than the grappling tactics of the Atakebune-based Japanese navy.
- Ohama Kagetaka, a pirate who used an atakebune
- Stephen Turnbull, "Samurai Warfare" (London, 1996), Cassell & Co ISBN 1-85409-280-4, p.102
- Stephen Turnbull, "Samurai Warfare" (London, 1996), Cassell & Co ISBN 1-85409-280-4, p.102f.
- Luis Frois, Historia de Japam. Edição anotada por Jose Wicki. 5 vols. Biblioteca Nacional de Lisboa, 1976-1984.
- Arai Hakuseki,「安宅御船仕様帖」「安宅御船諸色注文帖」,1711