ABSTRACT
The First World War had a more profound and more divisive effect upon the international socialist movement than any previous armed conflict. The international crisis which led to war was sparked off by the assassination of Francis Ferdinand, heir to the Habsburg throne, at Sarajevo in Bosnia on 28 June 1914. A fortnight earlier the French Socialist Party had held an extra-ordinary congress in Paris. Its debates were almost solely about the old problem of preventing war by a general strike, as proposed by Vaillant and Keir Hardie at the Copenhagen congress in 1910. In France, as in Germany, mass rallies for peace had been held at the end of July, organized by the Socialist Party and the CGT, the socialist trade union. The trend towards 'social-patriotism' became more marked in France during the first few weeks of war, under the emotional impact of the German invasion of Belgium and northern France, and the German army's advance on Paris.
