After nearly a century of political instability and warfare, Japan was on the verge of unification by Oda Nobunaga, who had emerged from obscurity in the province of Owari (present-day Aichi Prefecture) to dominate central Japan. In 1582, Oda was assassinated by one of his generals, Akechi Mitsuhide, and allowed Toyotomi Hideyoshi the opportunity to establish himself as Oda's successor after rising through the ranks from "ashigaru" (footsoldier) to become one of Oda's most trusted generals. Toyotomi eventually consolidated his control over the remaining "daimyōs" but ruled as "Kampaku" (Imperial Regent) as his common birth excluded him from the title of "Sei-i Taishōgun." During his short reign as Kampaku, Toyotomi attempted two invasions of Korea. The first attempt, spanning from 1592 to 1596, was initially successful but suffered setbacks from the Joseon Navy and ended in a stalemate. The second attempt began in 1597 but was less successful as the Koreans, especially their navy, led by Admiral Yi Sun-Sin, were prepared from their first encounter. In 1598, Toyotomi called for retreat from Korea prior to his death.