When Vytautas turned against the Knights, Marquard fought against Lithuania in an attempt to conquer Samogitia. Marquard helped to negotiate the peace in the 1398 Treaty of Salynas and was able to bring 1,600 cavalry to support Vytautas in the 1399 Battle of the Vorskla River against the Golden Horde. The battle ended in a crushing defeat of the Lithuanians and Vytautas barely escaped alive. Of the Teutonic forces, only three knights escaped with a few low-rank soldiers.