Men bearing arms have played major, direct political roles in practically all societies. However, the precise roles they have played and responsibilities they have exercised vary. In historical perspective, the nature of military participation in politics has shifted. There is a geographic dimension to the spread of civilian control of the military. The Third World—Africa, Asia, Latin America and the Middle East—illustrates the clearest examples of military control of politics. Certain underlying characteristics of Third World countries appear to make them far more liable to widespread, frequent or extensive military participation in politics. High income is not a prerequisite for civilian control of the military—China and India provide striking examples to the contrary—but seems to be highly correlated with relatively restricted political roles for the armed forces. "Boundary fragmentation" between the military and social classes or ethnic groups helps draw military officers into political roles.