When the Novgorodians turned to Poland–Lithuania for help in limiting Moscow's growing power, Ivan III and the metropolitan accused them not only of political treachery, but of attempting to abandon Eastern Orthodoxy and go over to the Catholic Church.

A draft treaty between Novgorod and the Grand Duke of Lithuania and King of Poland, Casimir IV Jagiellon (r. 1440–1492), said to have been found in a cache of documents after the battle of Shelon, made it clear that the Lithuanian Grand Prince was not to interfere with the election of the archbishop of Novgorod or the Orthodox faith in the city (by building Catholic churches in the city for example.

)[1] The battle took place in the morning of 14 July on the left bank of the Shelon River, which flows into Lake Ilmen southwest of Novgorod.

[2] Indeed, the Novgorodian Fourth Chronicle reports that Feofil, Archbishop-Elect of Novgorod, ordered his cavalry to not attack the Muscovites, but only the Pskovian forces, thus limiting their room to maneuver.

However, he only took direct control of the city-state in January 1478 after further strained relations with Archbishop Feofil and Novgorodian boyars led him to send his armies against the city in the winter of 1477–1478.