Hessian War died out, and peaked after 1645 in the Hessian War proper. This open warfare began with the Siege of Marburg in 1645 and ended in April 1648 (but before the Treaty of Westphalia which was concluded later that year and ended the Thirty Years' War) with victory going to Hesse-Cassel. In the aftermath, Upper Hesse was divided and parts of its territory went to the now stronger Hesse-Cassel. At a European level the Hessian War must be viewed in the larger context of the Thirty Years' War, in which the reformed Hesse-Cassel sided with the Protestant Swedish party, whilst Hesse-Darmstadt,
Treaty of Grimnitz Sweden refused to hand over the duchy. An agreement was reached to partition the duchy into a Swedish and a Brandenburgian part in the Peace of Westphalia (1648), which was put into effect in the Treaty of Stettin (1653). Treaty of Grimnitz The Treaty of Grimnitz (26 August 1529) was the final settlement of a long-standing dispute between the House of Pomerania and the House of Hohenzollern regarding the legal status and succession in the Duchy of Pomerania. It renewed and amended the Treaty of Pyritz of 1493. With some formal caveats, the House of Pomerania received the Duchy of