What did Marx and Engels do?

Marx and Engels did much with their lives, they were actively involved in political struggle from the early 1840's to the end of their lives. They helped to establish the First International and even fought in France in the revolution of 1848. But they are of course most well remembered for their writings, Marx primarily wrote on political economy and Engels primarily wrote on philosophy but they also wrote on history, politics generally and much else. Together they wrote The Communist Manifesto and several other works such as The German Ideology.