Magnus IV of Sweden
Kokemäki Castle was the administrative centre of Kokemäenkartano slottslän. Its function was similar to that of the castles of Turku, Häme and Vyborg, which are still preserved today. The only known reference to Kokemäki Castle is King Albert's warrant for the demolition and relocation of the castle, dated 12 July 1367. It was probably built of limestone and equipped with a round tower. In 1364–65 Kokemäki Castle was besieged by the army of King Albert as the castle was under the rule of Magnus IV of Sweden.