4 August 1914 was a decisive turning point for the socialist movement. The capitulation of the majority of parties of the Second International to pro-war chauvinism exposed a fundamental division between reformists and revolutionaries.

This talk will examine the developments in the socialist movement that explain the abandonment of an anti-war standpoint by the leadership of key parties such as the German Social Democratic Party. It will then focus on Lenin's role in attempting to develop a principled anti-war standpoint and lay the basis for a working class movement to end both the war and the capitalist system that breeds wars.