  The break came in 1914 when WW1 erupted and the SPD voted in favour of war credits, de facto embracing crude nationalism at the expense of the internationalist promise of concern for the whole working class regardless of national boundaries. Workers once united against capitalists would now kill each other at the border under different flags. Together with Franz Mehring, Klara Zetkin, and Karl Liebknecht, the only SPD deputy in the Reichstag to have opposed war credits until the end, Luxemburg founded the Spartakus group – initially part of the USPD (Unabhängige Sozialdemokratische Partei Deutschlands) the anti-war splinter faction from the SPD – and which was also known as the International group after Die Internationale, the joint publication which agitated for an end to the war and developing working class struggle against capitalism on an international basis. Soon after, Luxemburg was imprisoned, released, and then imprisoned again. Behind bars, she wrote “The Crisis of Social Democracy” better known as the Junius pamphlet or Juniusbrochüre because of the pseudonym Junius under which it appeared. It was the synthesis of a life’s critique of the limits of liberal parliamentarism, the pursuit of compromise for compromise’s sake, and the consequences of a failure to commit to principled internationalism on the side of social democratic parties which were organised on a national basis.