He joined the Bolsheviks in 1906 and was exiled from Russia from 1911 until just before the Russian Revolution, writing several books and editing the newspaper Novy Mir with Trotsky and Kollontai. During the war he was responsible for writing a small book on imperialism upon which many of the ideas in Lenin's better known work were based. On his return to Russia in August 1917 he became one of the leading Bolsheviks in Moscow and was elected to the Central Committee. After the revolution he also became editor of Pravda.
Bukharin led the opposition of the Left-Communists to the Treaty of Brest-Litovsk, arguing instead for the Bolsheviks to move the war effort to become a world-wide push for Proletarian Revolution. He later changed his position and accepted Lenin's policies, encouraging the development of the New Economic Policy in 1921. Such a drastic change of position from left to right would seem to suggest that Lenins comment that Bukharin had never fully understood dialectics was correct. He became a full member of the Politburo in 1924 and president of the Communist International (Comintern) in 1926.
After 1926 Bukharin, now regarded as leading the right of the Communist Party, became an ally of the centre of the party led by Stalin's which constituted the ruling group after Stalin had broken his earlier alliance with Kamenev and Zinoviev. It was Bukharin who developed the thesis of Socialism in one country which argued that Socialism, in Marxist theory the lower stage of Communism, could be developed in a single country. This new idea meaning that revolution need no longer be encouraged in the capitalist countries as Russia alone could achieve socialism. The thesis would become a hallmark of Stalinism long after Bukharin had died in the purges of the 1930s.
When he opposed Stalin's proposed collectivization of agriculture in 1928, he lost his Politburo post within a year. Arrested in 1937, Bukharin was tried in March 1938 as part of the Trial of the Twenty One for conspiring to overthrow the Soviet state. He made a 'confession' and was shot by the NKVD.
He was officially rehabilitated by the Russian state in 1988.