At the party conference held in London in 1903, there was a dispute between Lenin and Julius Martov. Lenin argued for a small party of professional revolutionaries with a large fringe of non-party sympathizers and supporters. Martov disagreed believing it was better to have a large party of activists. Leon Trotsky commented that "the split came unexpectedly for all the members of the congress. Lenin, the most active figure in the struggle, did not foresee it, nor had he ever desired it. Both sides were greatly upset by the course of events." Martov won the vote 28-23 but Lenin was unwilling to accept the result and formed a faction known as the Bolsheviks. Those who remained loyal to Martov became known as Mensheviks.

Vera Karelina joined the Bolsheviks. She was also a member of the Assembly of Russian Workers that had been established by Father Georgi Gapon in 1903. Within a year it had over 9,000 members. According to Cathy Porter: "Despite its opposition to equal pay for women, the Union attracted some three hundred women members, who had to fight a great deal of prejudice from the men to join." Vera Karelina led its women's section: "I remember what I had to put up with when there was the question of women joining... There wasn't a single mention of the woman worker, as if she was non-existent, like some sort of appendage, despite the fact that the workers in several factories were exclusively women." However, she thought the organisation was more effective than the Bolsheviks. She complained "how little our party concerned itself with the fate of working women, and how inadequate was its interest in their liberation.'' Gapon was impressed with Vera who believed she was "a woman of extraordinary spiritual force that can become the head of the female proletariat".

1904 was a bad year for Russian workers. Prices of essential goods rose so quickly that real wages declined by 20 per cent. When four members of the Assembly of Russian Workers were dismissed at the Putilov Iron Works, Gapon called for industrial action. Over the next few days over 110,000 workers in St. Petersburg went out on strike. Tsar Nicholas II became concerned about these events and wrote in his diary: "Since yesterday all the factories and workshops in St. Petersburg have been on strike. Troops have been brought in from the surroundings to strengthen the garrison. The workers have conducted themselves calmly hitherto. Their number is estimated at 120,000. At the head of the workers' union some priest - socialist Gapon. Mirsky came in the evening with a report of the measures taken."

In an attempt to settle the dispute, Father Georgi Gapon decided to make a personal appeal to Nicholas II. He drew up a petition outlining the workers' sufferings and demands. This included calling for a reduction in the working day to eight hours, an increase in wages and an improvement in working conditions. Gapon also called for the establishment of universal suffrage and an end to the Russo-Japanese War. Gapon wrote: "We workers, our children, our wives and our old, helpless parents have come, Lord, to seek truth and protection from you. We are impoverished and oppressed, unbearable work is imposed on us, we are despised and not recognized as human beings. We are treated as slaves, who must bear their fate and be silent. We have suffered terrible things, but we are pressed ever deeper into the abyss of poverty, ignorance and lack of rights."

Over 150,000 people signed the petition and on 22nd January, 1905, Gapon led a large procession of workers to the Winter Palace in order to present the petition. Alexandra Kollontai was on the march and her biographer, Cathy Porter, has described what took place: "She described the hot sun on the snow that Sunday morning, as she joined hundreds of thousands of workers, dressed in their Sunday best and accompanied by elderly relatives and children. They moved off in respectful silence towards the Winter Palace, and stood in the snow for two hours, holding their banners, icons and portraits of the Tsar, waiting for him to appear."

Gapon later described what happened in his book The Story of My Life (1905): "The procession moved in a compact mass. In front of me were my two bodyguards and a yellow fellow with dark eyes from whose face his hard labouring life had not wiped away the light of youthful gaiety. On the flanks of the crowd ran the children. Some of the women insisted on walking in the first rows, in order, as they said, to protect me with their bodies, and force had to be used to remove them. Suddenly the company of Cossacks galloped rapidly towards us with drawn swords. So, then, it was to be a massacre after all! There was no time for consideration, for making plans, or giving orders. A cry of alarm arose as the Cossacks came down upon us. Our front ranks broke before them, opening to right and left, and down the lane the soldiers drove their horses, striking on both sides. I saw the swords lifted and falling, the men, women and children dropping to the earth like logs of wood, while moans, curses and shouts filled the air."

In the attack by the Cossacks over 100 workers were killed and some 300 wounded. Alexandra Kollontai observed the "trusting expectant faces, the fateful signal of the troops stationed around the Palace, the pools of blood on the snow, the bellowing of the gendarmes, the dead, the wounded, the children shot." She added that what the Tsar did not realise was that "on that day he had killed something even greater, he had killed superstition, and the workers' faith that they could ever achieve justice from him. From then on everything was different and new." The incident became known as Bloody Sunday and it has been argued that this event signalled the start of the 1905 Revolution.

Vera Karelina died in Leningrad in 1931.