1845. Even before the publication of his book, Engels moved to Brussels in late April 1845, to collaborate with Marx on another book, German Ideology. While living in Barmen, Engels began making contact with Socialists in the Rhineland to raise money for Marx's publication efforts in Brussels; however, these contacts became more important as both Marx and Engels began political organizing for the Social Democratic Workers' Party of Germany. Brussels The nation of Belgium, founded in 1830, was endowed with one of the most liberal constitutions in Europe and functioned as refuge for progressives from other countries. From 1845 to 1848, Engels and Marx lived in Brussels, spending much of their time organising the city's German workers. Shortly after their arrival, they contacted and joined the underground German Communist League. The Communist League was the successor organisation to the old League of the Just which had been founded in 1837, but had recently disbanded. Influenced by Wilhelm Weitling, the Communist League was an international society of proletarian revolutionaries with branches in various European cities. The Communist League also had contacts with the underground conspiratorial organisation of Louis Auguste Blanqui. Many of Marx's and Engels's current friends became members of the Communist League. Old friends like Georg Friedrich Herwegh, who had worked with Marx on the Rheinsche Zeitung, Heinrich Heine, the famous poet, a young physician by the name of Roland Daniels, Heinrich Bürgers and August Herman Ewerbeck all maintained their contacts with Marx and Engels in Brussels. Georg Weerth, who had become a friend of Engels in England in 1843, now settled in Brussels. Carl Wallau and Stephen Born (real name Simon Buttermilch) were both German immigrant typesetters who settled in Brussels to help Marx and Engels with their Communist League work. Marx and Engels made many new important contacts through the Communist League. One of the first was Wilhelm Wolff, who was soon to become one of Marx's and Engels's closest collaborators. Others were Joseph Weydemeyer and Ferdinand Freiligrath, a famous revolutionary poet. While most of the associates of Marx and Engels were German immigrants living in Brussels, some of their new associates were Belgians. Phillipe Gigot, a Belgian philosopher and Victor Tedesco, a lawyer from Liège, both joined the Communist League. Joachim Lelewel a prominent Polish historian and participant in the Polish uprising of 1830–1831 was also a frequent associate. The Communist League commissioned Marx and Engels to