What did Karl Marx (1818-1883) and Friedrich Engels (1820-1895) say in the 'The Communist Manifesto' (1848) about the Revolution?

-Marx and Engels said Revolution was Inevitable, due to a Contradiction existing within Capitalism. Marx said his Form of Socialism avoids the Utopian Idealism of Earlier Forms and rather claims Historical Materialism (Change in Society due to Conflict between Classes) involves Scientific Analysis of Human Society -He based his Studies on history and dialectics (Conflicts due to Class) and concluded the Inevitability of Socialism can be Proved, as not a Desirable Aim.