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. 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 propulsion via sails.
