Those were only the biggest groups. Anarchists, syndicalists and a specifically Jewish leftist group, the Bundists, all competed with, fought against and sometimes allied with one another.

When war broke out in Europe in the summer of 1914, most of these groups, despite their opposition to the czarist regime, had supported what they saw as a defensive war caused by the aggression of the Central Powers, Germany and Austria-Hungary. In this, they were similar to a majority of European socialist and social-democratic parties, which abandoned their professed internationalism and rallied around the flags of their national governments.

Among the minority of political leaders who opposed the war, the most important was Lenin, along with the leaders of the left-wing strand of the Mensheviks, Yuli Martov and Leon Trotsky, all of whom were in exile. From faraway Zurich, Lenin could do little but write denunciations of the “social chauvinists” who supported the war.

As the war dragged on, however, support ebbed among both the political class and the Russian people. The Brusilov offensive of 1916, hailed as a great victory at the time, ended with as many as a million Russians killed or wounded, with nothing of substance in the course of the war changed. Czar Nicholas’s decision to take personal command of the Russian armed forces produced even greater disasters, discrediting both Nicholas and the monarchy as a whole.

The rapid collapse of the regime was, therefore, not surprising. But having come so suddenly to power, the provisional government faced the usual problem of revolutionary regimes: how to satisfy the often contradictory expectations of the people who had put them in power.

The provisional government rapidly introduced reforms that would have seemed utterly transformative in peacetime, instituting universal suffrage and freedoms of speech, assembly, press and religion, and addressing the demands of the many national minorities who made up much of the Russian empire’s population. But none of this delivered the three things the people wanted most: peace, bread and, for the peasants, land.

Of these failures, the most important was the failure of peace. The war continued, and in April it emerged that Milyukov had sent a telegram to the British and French governments, promising continued Russian support. He lost office shortly thereafter, and the Socialist Revolutionary leader Kerensky emerged as his successor.