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,
War of the Spanish Succession was reliant on the so-called "Maritime Powers" (England and the Dutch Republic) and also a higher priority for them. By formalising religious divisions within the Empire, the [[Peace of Westphalia|1648 Peace of Westphalia]] weakened its integrity and by 1700, the larger German states were pursuing their own policies. [[Electorate of Bavaria|Bavaria]] allied itself with France while as King of Poland, [[Augustus II the Strong|Augustus of Saxony]] was fully occupied by the [[Great Northern War]]. To gain [[Frederick I of Prussia|Frederick of Prussia]]'s support, Leopold recognised him as King, with Prussia made an equal member of the Grand Alliance. [[George I