The Communist League was the first Marxist international organisation. It was founded originally as the League of the Just by German workers in Paris in 1836. This was initially a utopian socialist and Christian communist grouping devoted to the ideas of Gracchus Babeuf. It became an international organisation, which Karl Marx, Friedrich Engels and Johann Eccarius later joined.
The League of Justs participated in the Blanquist uprising of May 1839 in Paris. Hereafter expelled from France, the League of the Just moved to London where they founded a front group, the Educational Society for German Working-men, in 1840. While Weitling moved to Switzerland, Bauer and Schapper escaped to London.
The League of Outlaws numbered approximatively 100 in Paris and 80 in Frankfurt, but by 1847 its successor the League of the Just numbered about 1,000, including members in Latin America.
Wilhelm Weitling's 1842 book, Guarantees of Harmony and Freedom, which criticized private property and bourgeois society, was one of the bases of the League of Just's social theory.
The Communist League held a second congress, also in London, in November and December 1847. Both Marx and Engels attended, and they were mandated to draw up a manifesto for the organisation. This became The Communist Manifesto.
The League was not able to function effectively during the 1848 revolution, despite temporarily abandoning its clandestine nature. The Workers' Brotherhood was established in Germany by members of the League, and became the most significant revolutionary organisation there. During the revolution Marx edited the radical journal the Neue Rheinische Zeitung. Engels fought in the Baden campaign against the Prussians (June and July 1849) as the aide-de-camp of August Willich.
The Communist League reassembled in late 1849, and by 1850 they were publishing the Neue Rheinische Zeitung Revue journal, but by the end of the year, publication had ceased amid disputes between the leading members of the group. In 1852, the organisation was ended formally.
In 1850, the German master spy Wilhelm Stieber broke into Marx's house and stole register of the League's members, which he sent to France and several German states. This caused the imprisonment of several members.