Krylenko was an exponent of socialist legality and the theory that political considerations, rather than criminal guilt or innocence, should guide the application of punishment. Although a participant in the Show Trials and political repression of the late 1920s and early 1930s, Krylenko was ultimately arrested himself during the Great Purge. Following interrogation and torture by the NKVD, Krylenko confessed to extensive involvement in wrecking and anti-Soviet agitation. He was sentenced to death by the Military Collegium of the Soviet Supreme Court, in a trial lasting 20 minutes, and executed immediately afterwards.
Krylenko was born in Bekhteyevo, in Sychyovsky Uyezd of Smolensk Governorate, the eldest of six children (two sons and four daughters) born to a populist revolutionary who, needing money to support his growing family, became a tax collector for the Tsarist government.
He joined the Bolshevik faction of the Russian Social Democratic Labor Party in 1904 while studying history and literature at St. Petersburg University where he was known to fellow students as Comrade Abram. He was a member of the short lived St. Petersburg Soviet during the Russian Revolution of 1905 and a member of the Bolshevik St. Petersburg Committee. He had to flee Russia in June 1906, but returned later that year. Arrested by the Tsar's secret police in 1907, he was released for lack of evidence, but soon exiled to Lublin without trial.
Krylenko returned to St. Petersburg in 1909, finishing his degree. He left the RSDLP in 1911, but soon rejoined it. He was drafted in 1912 and made Second Lieutenant before being discharged in 1913. After working as an assistant editor of Pravda and a liaison to the Bolshevik faction in the Duma for a few months, Krylenko was again arrested in 1913 and exiled to Kharkiv, where he received a law degree. In early 1914, Krylenko learned that he might be re-arrested and fled to Austria. At the outbreak of World War I in August 1914, he had to move to Switzerland as a Russian national. In the summer of 1915 Vladimir Lenin sent Krylenko back to Russia to help rebuild the Bolshevik underground organization. In November 1915 Krylenko was arrested in Moscow as a draft dodger and, after a few months in prison, sent to the South West Front in April 1916.
After the February Revolution of 1917 and the introduction of elected committees in the Russian armed forces, Krylenko was elected chairman of his regiment's and then division's committee. On April 15 he was elected chairman of the 11th Army's committee. After Lenin's return to Russia in April 1917, Krylenko adopted the new Bolshevik policy of irreconcilable opposition to the Provisional Government. He consequently had to resign his post on May 26, 1917 for lack of support from non-Bolshevik members of the Army committee.