Sosnovsky was one of the signatories of
The Declaration of 46, and supported
Leon Trotsky in the power struggle that followed the death of
Lenin, despite their differences on cultural issues. (Trotsky defended Mayakovsky and Yesenin). Sosnovsky's opposition to the party leadership was based on economics: he believed that the communist party needed to act against the growing influence of kulaks, whom he accused of exploiting and intimidating poorer peasants. He was dismissed form the editorship of
Bednota in 1924, but was allowed to continue working as a journalist on
Pravda. He was one of "75 active leaders of the Trotskyist Opposition" expelled from the communist party during its 15th Congress, in December 1927. After his expulsion, Sosnovsky was made to leave Moscow and take up a post in
Barnaul. In exile, he was one of the last Trotskyists to capitulate and ask to be reinstated in the party. When the group led by
Grigory Zinoviev surrendered, he wrote a scathing letter to
Illarion Vardin, one of Zinoviev's supporters, citing what he said was a Jewish funeral custom: In the latter part of 1928, when Stalin turned party policy sharply to the left, initiating a campaign against the kulaks, with Trotsky sent into enforced exile in Turkey, Sosnovsky was the leading voice among the remaining left oppositionists arguing that this was a "temporary manoeuvre" by Stalin, not a genuine turn to the left. He studied local conditions in Barnaul, where he calculated that just eight per cent of peasants were wealthy enough to own a threshing machine, which made the majority utterly dependent on them because In May 1929, four letters that he had written in exile were published abroad in Trotsky's
Bulletin of the Opposition. The
OGPU appear to have known about these letters being smuggled abroad, because Sosnovsky was arrested in Barnaul on 29 April 1929, and in May he was sentenced to three years in prison, and transferred to an "isolator" in
Chelyabinsk. By the end of 1929, after most of the leading Trotskyists, including
Yevgeni Preobrazhensky and
Karl Radek, had capitulated to Stalin, Sosnovsky was, after
Christian Rakovsky, the best known oppositionist still holding out in exile. In January 1930, the
Bulletin of the Opposition reported that Sosnovsky was editing a magazine
Pravda Behind Bars produced by imprisoned Trotskyists. Sosnovsky was then transferred to an "isolator" in
Tomsk In April 1932, he was sentenced to a further two years in prison. == Final years ==