In 1875 he was arrested but escaped from custody and over the next couple of years attempted to organize a peasant insurrection.
Deich joined the Land and Liberty and when it split into two factions, he joined the Black Repartition group that supported a socialist propaganda campaign among workers and peasants. The majority of members, joined People's Will, the group that favoured terrorism.
In 1880 Deich and other leaders of the Black Repartition group, including George Plekhanov, Vera Zasulich and Pavel Axelrod went to live in Geneva. Three years later they formed the Liberation of Labour group.
While in Germany in 1884 Deich was arrested and extradited for trial by a Russian court for a terrorist offence he had committed in 1876. Found guilty he was sentenced 13 years hard labour in Siberia.
Deich escaped from prison in 1901 and became active in the Social Democratic Labour Party. At the Second Congress of the Social Democratic Party in London in 1903, there was a dispute between Vladimir Lenin and Jules Martov, two of the party's main leaders. Lenin argued for a small party of professional revolutionaries with a large fringe of non-party sympathizers and supporters. Martov disagreed believing it was better to have a large party of activists. Martov won the vote 28-23 but Lenin was unwilling to accept the result and formed a faction known as the Bolsheviks. Those who remained loyal to Martov became known as Mensheviks.
After the February Revolution Deich returned to Petrograd and joined George Plekhanov in editing Edinstvo (Unity). He also wrote his memoirs and edited a volume of documents associated with the Liberation of Labour group.
Lev Deich died in 1941.