The February Revolution was a spontaneous eruption (not led by any one party) that destroyed the three hundred year power of Tsarism in a few days. The old order was wrecked, the Tsar resigned - what was to take its place?

Many revolutionaries thought their main task was over. They had overthrown a system that had defied change for generations. All they had to do was set up the "normal, civilised" institutions that existed in the rest of Europe - democracy and a Parliament accountable to the people.

But capitalism was far from being in a "normal, civilised" phase. It was in the throes of World War. Tsarism had been overthrown because of social problems - the devastating massacres of the First World War, the associated famine among the civilian population and the age-old injustices to the peasantry who still had no land to call their own. All the social issues were inflamed by War. They had not gone away. In the April Theses, Lenin reoriented the Bolsheviks towards socialist revolution as the only solution for the mass of the population.

Who was actually running the show after the Tsar had fled? The February Revolution was essentially the act of the Petrograd working class and the peasants, now soldiers in Petrograd barracks. They set up Soviets, organs of workers' and peasants' power. They were the real power in the land.

But these Soviets were dominated in the first days by reformists of different stripes. They believed the tasks of the revolution had basically been accomplished. All that was needed was consolidation. So they handed back power to a totally unelected Provisional Government, composed of various politicians who had historically opposed Tsarism. Russia after February was in a situation of dual power.

At this time the Bolsheviks were a tiny minority. They had 8,000 members; Trotsky estimates they had 3% support in the Soviets in the beginning of the revolution. How were they to make headway in a situation where Russia was on a knife-edge and could move forward towards revolution or back to counter-revolution in months?

They had two things going for them. First Lenin had rearmed the Party and pointed to the need for socialist revolution. And secondly the Provisional Government was totally incapable of solving the problems of working people.

• They wanted peace - but the allies in the west were demanding an offensive. Anglo-French imperialism wanted Russian soldiers to lay down their lives so they could gain a respite on the Western Front.
• They wanted bread - but the chaos of war meant the bread ration in the big cities was cut and cut.
• The peasants wanted land - but the old Tsarist state apparatus still ruled in the villages.

So the Bolsheviks formulated transitional demands: "Peace, Bread, Land" to express the needs of the masses and point the way to a new and better society. The Bolsheviks did not just abstractly argue that socialism was necessary. They used these demands to skilfully intervene in the movement and to show that simple, basic needs were incompatible with the continued existence of capitalism.

After April the Provisional Government consisted of ministers from openly capitalist parties and ministers from the reformist, nominally socialist, parties that dominated the Soviets.

The Bolsheviks did not just denounce the reformists as frauds. Instead they put them on the spot. They launched the demand, "Down with the ten capitalist ministers," a demand upon the reformists to break the coalition between capitalists and the representatives of the workers and peasants and to run the country in the interests of those the reformists purported to represent.

They also first raised the slogan, "All power to the Soviets." At this stage the Soviets were firmly under the control of the reformists. The Bolsheviks were demanding that the reformists push the capitalist politicians to one side and govern in the interest of the workers and peasants. The Bolsheviks were going with the grain of what the masses thought needed doing and directing them towards the socialist goal.

In June the First All-Russian Congress of Soviets met. The Bolsheviks had the support of about one fifth of the delegates. The Bolshevik supporters, especially among the soldiers, wanted to demonstrate against the futile offensive demanded by Britain and France. The Soviet Congress demanded the demonstration be cancelled.

Then the reformists pushed their luck too far. They called for a demonstration on June 18th to show the strength of "democracy". 400,000 people turned up. The vast majority were carrying banners with Bolshevik slogans.

Through correct perspectives and skilful tactics the Bolsheviks had made the breakthrough from sect to the only serious opposition Party to the Provisional Government and the reformists in the Soviet, and to the chaos of capitalism.

• The Significance of Lenin's April Theses 1917 by Darral Cozens (April 17, 2007)