 Although Alexander I was brought to the throne in 1400 by the Hungarians (with assistance from Mircea I of Wallachia), this ruler shifted his allegiances towards Poland (notably engaging Moldavian forces on the Polish side in the Battle of Grunwald and the Siege of Marienburg), and placed his own choice of rulers in Wallachia.His reign was one of the most successful in Moldavia's history.For all of his success, it was under the reign of Alexander I that the very first confrontation with the Ottoman Turks took place at Cetatea Albă in 1420.