Volume 9 of the Collected Works of Karl Marx and Frederick Engels is the last in the group of three volumes which show the activities of the founders of scientific communism during the revolutionary years 1848 and 1849. It covers the period from March 6, 1849 to August 1849.Like volumes 7 and 8, this volume consists in the main of articles written by Marx and Engels for the Neue Rheinische Zeitung, an organ of German and European democracy, and in particular of its revolutionary proletarian wing. It was during the last stage of the revolution, when the objective preconditions for uniting the proletariat and creating a proletarian mass party began to take shape, that the proletarian trend of the paper edited by Marx and Engels became especially pronounced. During this period the Neue Rheinische Zeitung played an increasingly important role as the legal centre which directed the activity of the Communist League members and inspired the revolutionary actions of the proletarian masses.