A revolutionary wave or revolutionary decade is one series of revolutions occurring in various locations within a similar time-span. In many cases, past revolutions and revolutionary waves have inspired current ones, or an initial revolution has inspired other concurrent "affiliate revolutions" with similar aims.
The causes of revolutionary waves have become the subjects of study by historians and political philosophers, including Robert Roswell Palmer, Crane Brinton, Hannah Arendt, Eric Hoffer, and Jacques Godechot.
Writers and activists, including Justin Raimondo and Michael Lind, have used the phrase "revolutionary wave" to describe discrete revolutions happening within a short time-span.
Mark N. Katz identified six forms of revolution;
rural revolution
urban revolution
Coup d'état, e.g. Egypt, 1952
revolution from above, e.g. Mao's Great Leap Forward of 1958
revolution from without, e.g. the allied invasions of Italy, 1944 and Germany, 1945.
revolution by osmosis, e.g. the gradual Islamization of several countries.
These categories are not mutually exclusive; the Russian revolution of 1917 began with urban revolution to depose the Czar, followed by rural revolution, followed by the Bolshevik coup in November. Katz also cross-classified revolutions as follows;
Central; countries, usually Great powers, which play a leading role in a Revolutionary wave; e.g. the USSR, Nazi Germany, Iran since 1979.
Aspiring revolutions, which follow the Central revolution
subordinate or puppet revolutions
rival revolutions, e.g. communist Yugoslavia, and China after 1969
Central and subordinate revolutions may support each other militarily, as for example the USSR, Cuba, Angola, Ethiopia, Nicaragua and other Marxist regimes did in the 1970s and 1980s.
A further dimension to Katz's typology is that revolutions are either against (anti-monarchy, anti-dictatorial, anti-capitalist, anti-communist, anti-democratic) or for (pro-fascism, pro-liberalism, pro-communism, pro-nationalism etc.).