The Muscovite army is successful in expanding into the Ukraine and a peace with Moscow, guaranteed by a marriage between Alexander and Helena, Ivan’s daughter, becomes a priority for Lithuania.

An "eternal" peace treaty is concluded on February 5, 1494.

The agreement marks 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 is estimated to be approximately eighty-seven thousand square kilometers (thirty-four thousand square miles).

A day after the official confirmation of the treaty, Alexander Jagiellon is betrothed to Helena (the role of the groom is performed by Stanislovas Kęsgaila).

Helena's Orthodox faith creates a number of complications.

Alexander has to receive a special permission from Pope Alexander VI to marry a non-Catholic and sign a formal agreement with Ivan III in October 1494 that Helena will not be forced to convert.

Alexander wants to add that if she wishes so herself, Helena can convert, but Ivan III adamantly rejects the amendment.

Ivan leaves Helena with detailed instructions on how to behave, who to invite for lunch, and where to pray (she is prohibited from visiting Catholic churches).

Ivan also requests that Alexander build an Orthodox church in Vilnius Castle Complex.