International politics were driven by the demands of the dominant economic system of the day, so* imperialist powers were supplying weapons for the RUP’s brutal activities, and* were** paid back in diamonds that were** taken out of the ground by Africans***, who were paid peanuts. * Typically when breaking up a sentence with a comma, it's used before the conjunction (so/and). ** Added "were" twice but I'm not sure exactly how to explain why. It just sounds better. The first "were" is for the imperialist powers, and the second one was for diamonds. *** Made African plural. Otherwise it implies that diamonds were taken out of the ground by the country itself rather than the people.