In 1914, the German Social-Democratic Party was the most powerful party of the Second International. With more than one million members, it was the largest single political party in Europe and the largest party in any European parliament. Socialists throughout the world, faced with the threat of war in the last days before that fateful 4th August, waited for the SPD to live up to its solemn commitments made at the International's congresses at Stuttgart and Basel, and oppose the war. Yet on 4th August, the SPD parliamentary fraction voted for the Imperial government's war credits, and the way to war was open.

How the German Party degenerated in the years leading up to 1914 to the point where it betrayed its most fundamental principles, and the struggle of the left in the party against this degeneration, is the subject of the article that follows.