 Complete the following phrase:  Geyso was born to a family of commoners in 1593 in Borken, Hesse. At an early age he was sent to a military academy in the Dutch Republic by Maurice, Landgrave of Hesse-Kassel, where he studied the art of war. He then joined a Swedish Banner which fought in the Ingrian War and the PolishSwedish War 160029 against Russia and Poland respectively. He then returned to the Holy Roman Empire, entering the service of rebellious Bohemian Estates who sparked the Thirty Years War through the Bohemian Revolt. He fought in the Battle of White Mountain, where he commanded a Fähnlein of infantry, while being in the rank of a captain. After the defeat of the Bohemians he continued to fight for the Protestant Union first under Ernst von Mansfeld, then Bernard of Saxe-Weimar as Rittmeister, finally entering the service of Christian IV of Denmark after the latter intervened into the war. In 1628, he fought as a colonel at the 