Metropolis of Kiev, Galicia and all Rus' (1441–1596)

[a] The canonical territory was the western part of the traditional Kievan Rus' lands — the states of the Grand Duchy of Lithuania and the Kingdom of Poland.

The episcopal seat was initially in the city of Navahrudak, which is today located in Belarus; later it moved to Vilnius in Lithuania.

The union was proclaimed on 6 July 1439 in the document Laetentur Caeli [3][b] which was composed by Pope Eugene IV and signed by the Holy Roman Emperor Sigismund and all but one of the bishops present.

[4] Sylvester Syropoulos[5] and other Greek writers charge Isidore with perjury because he accepted the union, despite his promise to Vasili II.

He also passed a message to Vasili II from the Holy See, containing a request to assist the metropolitan in spreading the Union in Rus'.

Like his immediate predecessors, he permanently resided in Moscow, and was the last Moscow-based primate of the metropolis to keep the traditional title with reference to the metropolitan city of Kiev.

While progress toward union in the East continued to be made in the following decades, all hopes for a proximate reconciliation were dashed with the fall of Constantinople in 1453.

Following their conquest, the Ottomans encouraged hardline anti-unionist Orthodox clerics in order to divide European Christians.

The Warsaw Confederation of 1573 secured the rights of minorities and religions;[16] it allowed all persons to practice any faith freely.

At the same time, colonization of the eastern territories (nowadays roughly western and central Ukraine),[17] heightened tensions among nobles, Jews, Cossacks (traditionally Orthodox), Polish and Ruthenian peasants.

In agreement with King Sigismund III Vasa, he deposed the Metropolitan Onesiphorus Devochka [ru; uk], probably because he was a digamy (the second marriage for priests) and he tolerated this use.

He wished to improve the mores of the clergy and to reduce of the meddling of lay people (and of confraternities) in the life of the Church and in monasteries.