[1] Smilga joined the Russian Social Democratic Labour Party (RSDLP) as a 14-year schoolboy, in January 1907, and was arrested for the first time during a May Day demonstration that year.

He was rearrested in July 1911, as a member of the illegal RSDLP organisation in the Lefortovo District, held in custody for three months, then deported to Vologda for three years.

[1] Freed as a result of the February Revolution, Smilga returned to Petrograd, and became a leading figure in the Bolshevik organisation in the Kronstadt naval base.

In May, he was Kronstadt's delegate to the Seventh Conference of the Bolshevik faction of the RSDLP, at which, despite his being only 24 years old, former fellow Siberian exiles put him forward as a member of the nine-member Central Committee.

Lenin was then hiding in Helsingfors, and "entered into a sort of conspiracy with Smilga", sending a long and angry letter on 27 September complaining that their fellow Bolsheviks were "passing resolutions" instead of "preparing their armed forces for the overthrow of Kerensky.

"[5] In mid-October, Smilga returned to Petrograd for the Congress of Northern Region Soviets, and stayed to help plan the Bolsheviks seizure of power.

Just before the October Revolution, he was sent back to Finland with orders to send 1500 armed sailors to Petrograd to act as reserves in case any troops from the front came to attack the city.

Smilga, Mikhail Lashevich and Sergei Gusev were political commissars on the Eastern Front, fighting the army of Admiral Kolchak.

At the Tenth party congress in March 1921, there was a secret session on why Russia lost the war, at which – according to Trotsky: Stalin came out with the declaration, equally startling in its viciousness and untruthfulness, that Smilga...had 'deceived the Central Committee' by 'promising' to take Warsaw by a definite date...I protested on the spot against this startling insinuation: Smilga's 'promise' meant merely that he had hoped to take Warsaw.

In December 1925, he was elected a full member of the Central Committee, although in August 1925, Stalin complained about Smilga's influence in Gosplan and denounced him as a "fake economic leader.

Trotskyist historian Pierre Broué suspected he was a member of the secret opposition bloc Trotsky, Zinoviev and Kamenev had created in 1932.

At the first of three Moscow show trials, in August 1936, the lead defendant Grigory Zinoviev named Smilga as having been implicated in the 'Trotskyite-Zinovievite Terrorist Centre'.

Unlike almost all the other eminent Old Bolsheviks named during the proceedings, he was never subjected to a public trial, suggesting that the NKVD had not been able to break his spirit sufficiently to be able to rely on him to confess.

A scientist working in Russia in the 1920s, who had no reason to speak well of Smilga, and in face held him responsible for the execution of a group of technicians from the former Nobel company during the civil war, nevertheless believed that he should have been appointed head of Vesenkha.

"He seemed to me quite superior to all other members of the Praesidium...He was well educated, with vigorous and pleasant features, and authoritative in speech and action...he impressed me favourably by his frankness and the fearless way he expressed his convictions, even when they were quite the opposite of those of his party colleagues.

"[18] Viktor Serge, a fellow supporter of the left opposition, described Smilga as "a fair-haired intellectual with spectacles, a chin-beard, and thinning front, ordinary to look at and distinctly the armchair sort.

"[19] Smilga's wife, Nadezhda Vasilievna Poluyan (1896-1937) was born into a Cossack farming family in Kuban joined the Bolsheviks in 1915, and was expelled from the party, as he was, in 1928 but later readmitted.