Back in St. Petersburg after three years of exile, Lenin threw himself into a new project–the creation of a Russian-language Marxist newspaper, to be called Iskra, meaning "The Spark." To this end, he traveled to Western Europe for the second time, and it was there, with Plekhanov's support, that he published the first issue on Christmas Eve of 1900. (Because of the restrictive nature of the Tsar's regime, Iskra was printed in Germany and then smuggled into Russia.) It was at this point that Lenin first adopted his revolutionary pseudonym, naming himself after the Lena, the longest river in Siberia.
Iskra soon occupied most of Lenin's hours, as he served both as its primary writer–he churned out thirty-two articles in the first two years, more than any other contributor–and as a key fundraiser. Between 1900 and 1903, he did not return to Russia, but instead traveled across Europe, writing articles, attending meetings, and giving speeches; he persisted in this itinerant lifestyle, with few interruptions, until 1917. Krupskaya, whose own exile ended early in 1901, soon joined her husband; she met him in Munich, where the first eight issues of Iskra were published. In the year following her arrival, Lenin devoted himself to a new book-length pamphlet, entitled What Is To Be Done?, which laid out his personal blueprint for Marxist revolution. This tract, advertised in Iskra, gained such notoriety that Lenin, Plekhanov, and the other editors decided to shift their base of operations out of Germany and into England, where they were less likely to be arrested and deported to Russia. The move was made in spring of 1902, and from then on Iskra was published out of London.
By 1903, when the Second Congress of the Social Democrats was held in London and Brussels, Lenin had become a major figure within the party, through his writings, his extensive contacts within the movement, and his position on the board of Iskra. At the Congress, however, divisions within the Social Democrats flared into the open, resulting in a decisive split within the party. The schism had been growing for some years, but Lenin had crystallized the differences in his What Is To Be Done?. In that pamphlet, he had declared that the revolution, when it came, would be carried out not by a broad popular movement, as Marx had predicted, but by an elite cadre of Marxists whose day-to-day work consisted of nothing but revolutionary activity. "The organization of the revolutionaries must consist first and foremost of people who make revolutionary activity their profession," he wrote. "Such an organization must perforce not be very extensive and must be as secret as possible... Give us an organization of revolutionaries, and we will overturn Russia!"
Lenin's opponents at the Congress, led by Y.O. Martov (himself a member of Iskra's editorial board), attacked this vision, and argued for a more broad-based party, rooted in popular support. When the decisive vote came over which standards to adopt for party membership, Martov's proposal actually won by a count of twenty-eight to twenty-two, but Lenin (who only obtained majorities by calling surprise votes on procedural matters) nevertheless called his faction the Bolsheviks, meaning "majority," and their adversaries the Mensheviks, meaning "minority." The names stuck, despite their inaccuracy, and from then on the Social Democrats, despite official unity, were divided into two hostile wings. Plekhanov at first sided with Lenin, and Martov and his fellow Mensheviks were removed from Iskra's board–but Lenin's strong-arm tactics and violent rhetoric (both of which were to become characteristic of the Bolsheviks) soon led Plekhanov to reconsider, and by autumn of 1903 Mensheviks outnumbered the Bolsheviks on the paper's board. Dismayed by this turn of events, Lenin resigned from Iskra in December, having moved to Geneva with Krupskaya.
The Social Democrats' Central Committee, of which Lenin was a member, continued to work for a compromise between the two wings throughout the spring and summer of 1904. Lenin was invited to return to Iskra, but he declined to do so, and instead called for another Party Congress, where he was convinced he could obtain a majority. When this demand was rebuffed, he resigned from the Central Committee, effectively ending the chance of a resolution to the party split. In winter of 1904, Lenin embarked on a modest speaking tour that took him to Paris and then back to Switzerland; at the same time, he founded a new journal, called Vperyod ("Forward!"), which first appeared in January of 1905, but would continue publication only until mid-May of that year. By that time, the gaze of Lenin and all his fellow Marxists had refocused on Russia, where revolution had suddenly broken out.