Александр Ягеллончик
In August 1492, shortly after the death of Polish King Casimir IV Jagiellon, Ivan III of Russia attacked the Grand Duchy of Lithuania, launching what would become a series of Muscovite–Lithuanian Wars. John I Albert became King of Poland while Alexander Jagiellon became Grand Duke of Lithuania. The Muscovite army was successful and a peace with Moscow, guaranteed by a marriage between Alexander and Helena, became a priority for Lithuania. An "eternal" peace treaty was concluded on 5 February 1494. The agreement marked the first Lithuanian territorial losses to Moscow: the Principality of Vyazma and a sizable region in the upper reaches of the Oka River – the lost area was estimated to be approximately . A day after the official confirmation of the treaty, Alexander Jagiellon was betrothed to Helena (the role of the groom was performed by Stanislovas Kęsgaila).