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 Fifth Coalition not been able to save Prussia. The Russian and French armies met in February 1807 at the savage and indecisive Battle of Eylau, which left behind between 30,000–50,000 casualties. Napoleon regrouped his forces after the battle and continued to pursue the Russians in upcoming months. The action in Poland finally culminated on 14 June 1807, when the French mauled their Russian opponents at the Battle of Friedland. The resulting Treaty of Tilsit in July ended two years of bloodshed and left France as the dominant power on the European continent. It also severely weakened Prussia and formed a Franco-Russian axis