He was taken captive in July 1384 by Vytautas, Grand Duke of Lithuania, after Vytautas reconciled with his cousin Jogaila during the Lithuanian Civil War (1381–1384). At the time Marquard was a castellan of New Marienburg, a Teutonic Castle on the Neman River. Marquard became a friend and close adviser of Vytautas, who sent him on diplomatic missions to establish alliance with the Knights when another civil war broke out in Lithuania in 1389. Marquard regained freedom and rejoined the Knights, becoming castellan of Ragnit and valued expert of Lithuanian affairs due to his fluent command of the Lithuanian language and intimate knowledge of the royal court.