This work is the first collection of source materials on Orthodox Church history published in the United States, and the first to specialize on the medieval doctrine of the Rus' Metropolitanate. More than 500 manuscript collections have been examined in archives in various cities: Moscow, St. Petersburg, Kyiv, Vilnius, Vladimir, Iaroslavl', Pskov, Smolensk, Minsk, Novosibirsk, and Tomsk; and microfilms were received from Warsaw, Cracow, and Rome. The publication presents over 250 documents in chronological order, including many not formerly known to scholars. In this way, all letters of the metropolitan chancery and the episcopal cathedrae of the fourteenth to early sixteenth centuries are made available together and in their original language.

For the first time, the sources of such events as the Church–State crisis in Moscow (1378–1381); the struggle of the Muscovite princes with Vitold for the preservation of the unity of the Metropolitanate (1415–1420); the division of the Metropolitanate of “Kyiv and all Rus’” into the Lithuanian (Kyivan) and Muscovite dioceses (1458–1460); the subjugation of Novgorod to Moscow (1478); the fate of Kyiv in the fourteenth and fifteenth centuries; the struggle of Ivan III with the Great Horde of Khan Akhmed (1480); and the history of the “Judaizer” heresy (1486–1504) are presented in a single collection.