Complex sentence: Teutonic War (1409--1411), the Prussian estates eagerly pledged allegiance to King Władysław II Jagiełło (Jogaila) of Poland, but they quickly returned to the order's rule after the Poles were unable to conquer Marienburg (Malbork).
Split into simpler sentences: Teutonic War (1409--1411), the Prussian estates eagerly pledged allegiance to King Władysław II Jagiełło (Jogaila) of Poland. But they quickly returned to the order's rule after the Poles were unable to conquer Marienburg (Malbork).