Križanić managed to secure permission from the papacy for a brief visit to Moscow from 25 October to 19 December 1647. as part of a Polish embassy. However, he was not able to secure permission for a prolonged stay until 1658 (it was retracted shortly after being issued, a fact that Križanić simply ignored) and he did not arrive in Moscow until 17 September 1659. Another author said that he pretended to be an Orthodox Serb. He was assigned the duty of translating Latin and Greek documents and preparing an improved Slavic grammar. However, he was exiled to Siberia on 20 January 1661. The reason for his exile is still unknown. Possible explanations put forward have included the fact that he was a Roman Catholic priest, his criticism of Russian society and of the Greeks, with whom Patriarch Nikon was attempting reconciliation, and other political and social motives. Križanić postulated that he was exiled because of "some foolish thing" he had said to someone, and that whatever he had said had been mentioned to the authorities.