High Quality Content by WIKIPEDIA articles! Aizuwakamatsu Castle ( , Aizuwakamatsu-j ?), also known as Tsuruga Castle ( Tsuruga-j ) is a traditional castle in northern Japan, at the center of the city of Aizuwakamatsu, in Fukushima Prefecture.The castle was constructed by Ashina Naomori in 1384, and was originally named Kurokawa Castle ( Kurokawa-j ). It was the military and administrative center of the Aizu region until 1868.Date Masamune, the greatest warlord of the T hoku area, had struggled against the Ashina clan for years, and finally captured the castle in 1589. But soon he submitted to Toyotomi Hideyoshi and gave it up in 1590.