In 1902, she left her husband, with whom she had an open marriage, to marry his younger brother Vladimir, who shared her radical political views, and bore him her fifth child, Andrei.

In 1903, she joined the illegal Russian Social Democratic Labour Party.
Armand distributed illegal propaganda; after her arrest in June 1907 she was sentenced to two years' internal exile in Mezen in Northern Russia.

In November 1908 Armand managed to escape from Mezen and eventually left Russia to settle in Paris, where she met Vladimir Lenin and other Bolsheviks living in foreign exile.
In 1911 Armand became secretary for the Committee of Foreign Organisations established to coordinate all Bolshevik groups in Western Europe.

Armand returned to Russia in July 1912.
This was a risky mission.
Lenin needed her to pass on the resolution of the Prague Conference, to help organise the Bolshevik campaign to get its supporters elected to the Duma, and find out what was going on in Pravda.
Helen Rappaport notes that Lenin knew her entry into Russia would invite immediate arrest, yet he made light of it, his concerns for party works overcoming his personal feelings for her.
 Two months later she was arrested and imprisoned, only to be released against bail in March 1913, thanks to Alexander's generous support.
Once again illegally leaving Russia, she went to live with Vladimir Lenin and Nadezhda Krupskaya in Galicia.
She also began work editing Rabotnitsa.
Krupskaya, with admiration, noted that exhausted as Armand was, she threw herself immediately into the party works.
Lenin wrote to her and trusted her more than anyone else in his circles.
The Okhrana considered Armand to be the right hand of Lenin.

According to author Ralph Carter Elwood, "Even more than Trotsky during the Iskra period, she became Lenin’s ‘cudgel’ — someone to beat wavering Bolsheviks back into line, to convey uncompromising messages to his political opponents, to carry out uncomfortable missions which Lenin himself preferred to avoid".

Armand was upset that many socialists in Europe chose not to fight against the war effort during World War I. She joined Lenin in helping to distribute propaganda that urged Allied troops to turn their rifles against their officers and to start a socialist revolution.

Lenin appointed her as the Bolshevik representative to the International Socialist Bureau conference in Brussels in July 1914.
Bertram Wolfe remarked, "He was sending her to meet and do battle with such large figures as Kautsky, Vandervelde, Huysmans, Luxemburg, Plekhanov, Trotsky and Martov.
He counted on her mastery of all the languages of the International, her literal devotion to him and his views, her steadfastness under fire".
He wrote to her:
I am convinced that you are one of those who develops, grows stronger, becomes more energetic and bolder when alone in a responsible post … I stubbornly disbelieve the pessimists who say that you — are hardly — nonsense and again nonsense.

In March 1915 Armand went to Switzerland where she organised the anti-war International Conference of Socialist Women.
In 1902, she left her husband, with whom she had an open marriage, to marry his younger brother Vladimir, who shared her radical political views, and bore him her fifth child, Andrei.
In 1903, she joined the illegal Russian Social Democratic Labour Party. Armand distributed illegal propaganda; after her arrest in June 1907 she was sentenced to two years' internal exile in Mezen in Northern Russia. 
In November 1908 Armand managed to escape from Mezen and eventually left Russia to settle in Paris, where she met Vladimir Lenin and other Bolsheviks living in foreign exile. In 1911 Armand became secretary for the Committee of Foreign Organisations established to coordinate all Bolshevik groups in Western Europe.
Armand returned to Russia in July 1912. This was a risky mission. Lenin needed her to pass on the resolution of the Prague Conference, to help organise the Bolshevik campaign to get its supporters elected to the Duma, and find out what was going on in Pravda. Helen Rappaport notes that Lenin knew her entry into Russia would invite immediate arrest, yet he made light of it, his concerns for party works overcoming his personal feelings for her.  Two months later she was arrested and imprisoned, only to be released against bail in March 1913, thanks to Alexander's generous support. Once again illegally leaving Russia, she went to live with Vladimir Lenin and Nadezhda Krupskaya in Galicia. She also began work editing Rabotnitsa. Krupskaya, with admiration, noted that exhausted as Armand was, she threw herself immediately into the party works. Lenin wrote to her and trusted her more than anyone else in his circles. The Okhrana considered Armand to be the right hand of Lenin. 
According to author Ralph Carter Elwood, "Even more than Trotsky during the Iskra period, she became Lenin’s ‘cudgel’ — someone to beat wavering Bolsheviks back into line, to convey uncompromising messages to his political opponents, to carry out uncomfortable missions which Lenin himself preferred to avoid".
Armand was upset that many socialists in Europe chose not to fight against the war effort during World War I. She joined Lenin in helping to distribute propaganda that urged Allied troops to turn their rifles against their officers and to start a socialist revolution.
Lenin appointed her as the Bolshevik representative to the International Socialist Bureau conference in Brussels in July 1914. Bertram Wolfe remarked, "He was sending her to meet and do battle with such large figures as Kautsky, Vandervelde, Huysmans, Luxemburg, Plekhanov, Trotsky and Martov. He counted on her mastery of all the languages of the International, her literal devotion to him and his views, her steadfastness under fire". He wrote to her:
I am convinced that you are one of those who develops, grows stronger, becomes more energetic and bolder when alone in a responsible post … I stubbornly disbelieve the pessimists who say that you — are hardly — nonsense and again nonsense.
In March 1915 Armand went to Switzerland where she organised the anti-war International Conference of Socialist Women.
Inessa Armand