Kiyosu Castle
During the Heian period, the province was divided into numerous "shōen" controlled by local samurai clans. However, by the Sengoku period, the province had fragmented into many small territories largely dominated by the Oda clan. Under Oda Nobunaga, the province was reunified. Nobunaga began his campaign to reunify Japan from his stronghold at Kiyosu Castle. and many of his retainers (who later became "daimyōs" under the Tokugawa shogunate) were natives of Owari, including Toyotomi Hideyoshi and Katō Kiyomasa.