He was known to have been one of the leaders of the
boyar party, which supported tsarevich
Dmitry Ivanovich (grandson of
Ivan III) in a struggle against
Sophia Paleologue's son
Vasili for succession to the throne. In ecclesiastic matters, the boyar party was generally closer to
heretical and freedom-loving circles. Vassian wrote the "Epistle on the Ugra" (
Poslanie na Ugru), which contains political propaganda about the so-called "
Stand on the Ugra". It argued that
Batu Khan had plundered and enslaved the land, usurping the title of
tsar without being "of a
tsarian family", alleging that his descendant
Ahmed Khan bin Küchük was a mere "brigand and savage and fighter-of-God", while insisting Ivan III was the only real, legitimate, Orthodox
tsar. Vassian wrote that the Tatar campaign (
nakhozhdenie) had made the Muscovites afraid, but the Church released Ivan from any oath made to Ahmed Khan, as it was made under duress, and so he no longer owed his
Golden Horde overlord any loyalty. The problem with this logic is that Rus' writers had traditionally translated both the Mongol title
khan and the Greek Byzantine title
basileus ('king, emperor') as
tsar (originally from
caesar), but Vassian was arguing only Christian Orthodox monarchs such as the Byzantine
basileus and the Muscovite
knyaz ('prince') should be called
tsars. Therefore, Vassian resolved that he needed to elevate the prince of Moscow to the status of
tsar, while claiming the
Chingisid khans must have been imposters, stealing the
tsar title they never deserved, even though Vassian thereby rejected the
Pauline doctrine invoked in the
Life of Alexander Nevsky and the
vita of
Michael of Chernigov. It is the first written political attempt to deny the legitimacy of the Golden Horde's supremacy over the Rus' principalities since the
Mongol invasion of Kievan Rus' in 1237–1242, and also the first Muscovite attempt to portray the 1480 Stand on the Ugra as having major ideological significance. Literary successors of Vassian's epistle would greatly exaggerate the standoff, wherein 'the events of 1480 assume the status of pivotal moments in the history of man.' In 1499, Ivan III found out about the
conspiracy against Vasili and ordered arrests (the tsar first favored Dmitry Ivanovich). Vassian Patrikeyev was forced to take monastic vows and sent to
Kirillo-Belozersky Monastery. ==Ecclesiastic career==