is a state of a severe disequilibrium that is responsible for revolutions. Finally, the third group, which included writers such as Charles Tilly, Samuel P. Huntington, Peter Ammann, and Arthur L. Stinchcombe followed the path of political sciences and looked at pluralist theory and interest group conflict theory. Those theories see events as outcomes of a power struggle between competing interest groups. In such a model, revolutions happen when two or more groups cannot come to terms within a normal decision making process traditional for a given political system, and simultaneously have enough resources to employ force in pursuing their goals. The second generation theorists saw the development of the revolutions as a two-step process; first, some change results in the present situation being different from the past; second, the new situation creates an opportunity for a revolution to occur. In that situation, an event that in the past would not be sufficient to cause a revolution (e.g., a war, a riot, a bad harvest), now is sufficient; however, if authorities are aware of the danger, they can still prevent a revolution through reform or repression. Many such early studies of revolutions tended to concentrate on four classic cases: famous and uncontroversial examples that fit virtually all definitions of revolutions, such as the Glorious Revolution (1688), the French Revolution (1789–1799), the Russian Revolution of 1917, and the Chinese Revolution (also known as the Chinese Civil War) (1927–1949). In his The Anatomy of Revolution, however, the Harvard historian Crane Brinton focused on the English Civil War, the American Revolution, the French Revolution, and the Russian Revolution. In time, scholars began to analyze hundreds of other events as revolutions (see List of revolutions and rebellions), and differences in definitions and approaches gave rise to new definitions and explanations. The theories of the second generation have been criticized for their limited geographical scope, difficulty in empirical verification, as well as that while they may explain some particular revolutions, they did not explain why revolutions did not occur in other societies in very similar situations. The criticism of the second generation led to the rise of a third generation of theories, with writers such as Theda Skocpol, Barrington Moore, Jeffrey Paige, and others expanding on the old Marxist class conflict approach, turning their attention to rural agrarian-state conflicts, state conflicts with autonomous elites, and the impact of interstate economic and military competition on domestic