After the war Trubetskoy became a
Freemason, a member of the Lodge of the Three Virtues. He was among the founders of the first proto-Decembrists societies - the
Union of Salvation (1816) and later the Union of Prosperity (1819). The two unions were largely based on freemasonry. They sought gradual improvement of the
Russian Empire, but had not adopted some goals the Decembrists did later: complete abolition of
serfdom, introduction of constitution and constitutionally secured liberties, abolition of privileges of upper
estates of the realm. In 1819 Trubetskoy went abroad for treatment. When he returned in 1821 he found the Union had ceased to exist. Trubetskoy was one of the founders and leaders of the Northern Society. Trubestkoy advocated
Constitutional monarchy, but other Decembrists desired revolution, to execute the tsar and establish a
republic (e.g.
Ryleev and
Pestel). He was elected "dictator" but did not come to
Senate Square, most probably because he expected the revolt to fail. He was arrested the next day at the apartments of Count Ludwig Lebzeltern, his
brother-in-law and the
Austrian Empire's
minister to St. Petersburg. ==Katorga and exile==