Its political success was closely linked to its capacity to mob ise oppressed or disadvantaged classes in sup- port of revolutionary leaders who were well organised and fol- lowed clear political strategies. Communism in power proved to be a formidable force: the construction of one-party states not only weakened class enemies' and opposition groups, but also allowed communist parties to operate as ruling parties in the sense that they dominated all aspects of government, the military the economy and the ideological apparatus. In practice, twenti- eth-century communism was largely a vehicle for modernisa- tion that was most successful in economically backward societies where its success was ultimately judged in terms of its capacity to deliver social development.