Franz Mehring was born in Schlawe, Germany, on 27th February, 1846. He became a journalist and worked for various daily and weekly newspapers including Neue Zeit, Die Zukunft and Frankfurter Zeitung. Mehring also edited the socialist newspaper, Berliner Volkszeitung.
Mehring supported August Bebel and Wilhelm Liebknecht when they voted against war credits in 1870: "There were still traces of a split in the Social Democracy when it came to voting the war credits in July, 1870; all the Social Democratic deputies voted favorably except Liebknecht and Bebel, who abstained from voting. When in December of the same year the second war credit was to be granted, all differences had disappeared, and every single parliamentary deputy voted. All the groups of the Social Democracy of that time lined up as a unit against the militarism of the class-controlled government, a stand to which the party has adhered ever since."
Mehring joined the Social Democratic Party in 1890 and soon became accepted as one of the SDP's theoreticians. In 1893 he published On Historical Materialism where he attempted to explain the theories of Karl Marx and Friedrich Engels: "The bourgeois world today regards historical materialism as it did Darwinism a lifetime ago, and socialism half a lifetime ago. It reviles it without understanding it.... The life work of Marx and Engels is based throughout on historical materialism; all their writings are founded upon this. It is simply a trick of the bourgeois pseudo-sciences to pretend that they made only occasional excursions into the science of history in order to find support for a theory of history."
Mehring was deeply influenced by the work of Rosa Luxemburg. Her biographer, Paul Frölich, pointed out: "Franz Mehring used Luxemburg's manuscript for the explanatory notes to his edition of the essays by Marx and Engels from the years 1848-49, and it is not difficult to distinguish and intellectual influence of Rosa Luxemburg in his work." In 1897 Mehring published The History of German Social Democracy.
The author of Rosa Luxemburg: Her Life and Work (1940) has argued: "Franz Mehring was a touchy and sensitive man given to nursing grudges. No wonder they were often clashing and breaking up... Nevertheless, their mutual respect for each other's intellectual achievements, their related temperaments, and finally their common aims and enemies brought them together again and again."
In 1911 Mehring warned against the dangers of war with Britain and France and called on the working-class to stop this from happening: "For the working class this helplessness no longer exists. They have an approved weapon with which to tear the question of peace and war from the hands of the diplomatists, in that they take this question into their own hands.... An old poet has said: When the kings quarrel the peoples get the blows. But if the peoples refuse to allow themselves to be flogged, kings will think twice before they quarrel. Certainly the peace policy of the workers cannot prevent a world-wide war under all conditions, but it can at least provide that such a way shall bring the ruin of those who have instigated it."
Karl Liebknecht was the only member of the Reichstag who voted against Germany's participation in the First World War. He argued: "This war, which none of the peoples involved desired, was not started for the benefit of the German or of any other people. It is an Imperialist war, a war for capitalist domination of the world markets and for the political domination of the important countries in the interest of industrial and financial capitalism. Arising out of the armament race, it is a preventative war provoked by the German and Austrian war parties in the obscurity of semi-absolutism and of secret diplomacy."
Clara Zetkin later recalled: "The struggle was supposed to begin with a protest against the voting of war credits by the social-democratic Reichstag deputies, but it had to be conducted in such a way that it would be throttled by the cunning tricks of the military authorities and the censorship. Moreover, and above all, the significance of such a protest would doubtless be enhanced, if it was supported from the outset by a goodly number of well-known social-democratic militants.... Out of all those out-spoken critics of the social-democratic majority, only Karl Liebknecht joined with Rosa Luxemburg, Franz Mehring, and myself in defying the soul-destroying and demoralising idol into which party discipline had developed."
Mehring now joined with Rosa Luxemburg, Leo Jogiches, Paul Levi, Ernest Meyer, Karl Liebknecht and Clara Zetkin to establish an underground political organization called Spartakusbund (Spartacus League). The Spartacus League publicized its views in its illegal newspaper, Spartacus Letters. Liebknecht, like the Bolsheviks in Russia, began arguing that socialists should turn this nationalist conflict into a revolutionary war.
In May 1915, Karl Liebknecht published a pamphlet, The Main Enemy Is At Home! He argued: "The main enemy of the German people is in Germany: German imperialism, the German war party, German secret diplomacy. This enemy at home must be fought by the German people in a political struggle, cooperating with the proletariat of other countries whose struggle is against their own imperialists. We think as one with the German people – we have nothing in common with the German Tirpitzes and Falkenhayns, with the German government of political oppression and social enslavement. Nothing for them, everything for the German people. Everything for the international proletariat, for the sake of the German proletariat and downtrodden humanity."
Rosa Luxemburg pointed out that it was important to stop the First World War through mass action. This brought her into conflict with Lenin who had argued that "the slogan of peace is wrong - the slogan must be, turn the imperialist war into civil war." Lenin believed that a civil war in Russia would bring down the old order and enable the Bolsheviks to gain power. Luxemburg and Leo Jogiches took the side of the Mensheviks in their struggle with the Bolsheviks. As a result Lenin favoured the Polish section led by Karl Radek over those of Luxemburg.
On 1st May, 1916, the Spartacus League decided to come out into the open and organized a demonstration against the First World War in the Potsdamer Platz in Berlin. One of those who attended reported: "It was a great success. At eight o'clock in the morning a dense throng of workers - almost ten thousand - assembled in the square, which the police had already occupied well ahead of time. Karl Liebknecht, in uniform, and Rosa Luxemburg were in the midst of the demonstrators and greeted with cheers from all sides." Several of its leaders, including Liebknecht and Luxemburg were arrested and imprisoned.