an agreement in 1596 that united with the Roman Catholic Church several million Ukrainian (Ukrainian Greek Catholic Church) and Belorussian Orthodox Christians living under Polish rule in Lithuania.

Inspired by the Council of Florence (Ferrara-Florence, Council of) (1438–39), which sought the reunion of all Eastern churches with Rome, the metropolitan of Kiev, Michael Ragoza, began negotiations with Catholic churchmen and the Polish king Sigismund III (Sigismund III Vasa), a Roman Catholic. At a synod held at Brest, the Ukrainian Orthodox hierarchy declared their wish to submit to Rome. The Polish monarchy, fearful of Russian influence, particularly through its Orthodox Church, also sought to unify the various peoples under its rule through Catholicism. Hence the King was pleased, and he promised the Ukrainian Orthodox the rights and privileges enjoyed by the Latin rite as well as the preservation of traditional Eastern rites and customs. These guarantees were proclaimed by Sigismund on Aug. 2, 1595; and in 1596 the terms of Pope Clement VIII and the King were accepted at another Orthodox synod at Brest, attended by the bishops of Vladimir, Lutsk, Polotsk, Pinsk, and Chelm, as well as the Metropolitan of Kiev.

A peaceful reunion, however, did not result. The bishops of Lvov and Przemyśl refused to comply, and Orthodox laymen founded brotherhoods to oppose union. The opponents of the Brest-Litovsk union felt that their tradition and autonomy were being given away and feared that the union would breed hybridism or the tendency toward Latinization and hence a betrayal of ancient and nationalistic tradition.