A revolution can be defined as many things. And many historians have attempted it in the past. The most accurate depiction of a revolution, in my opinion, was written by Chalmers Johnson in the 1960's. He stated that a revolution takes place when the dysfunction of an existing government and its decay gives rise to another power group taking control. I believe this to be most accurate because if a government were not dysfunctional or decaying, then it would be most difficult for an inferior group of power to effectively overthrow it. A revolutionary party would not have formed to start with if the government was doing an effective and satisfactory job of providing for its people.
Other theories of revolution include one by Crane Brinton, stating that revolution is a process. His idea of revolution was an overthrow of power, which led to extremists coming to power, then subsiding into a more moderate time. While this theory does a most proficient job of describing some revolutions, it is far to specific to define revolutions in a generalized perspective.
Karl Marx has had a very successful theory of revolution, one that has been used and modeled by many political and revolutionary leaders throughout history. Marx theorized that a revolution is a struggle between two antithetical elements. These two groups or classes clash, often violently, and it leads to a synthesis that results in socialism. Many leaders throughout history have changes or augmented the Marxist theory to fit their own revolutionary needs at that specific time. This theory is an excellent basis for all class-based revolutions, and Marxist type of revolutions have occurred throughout the twentieth century. .
In 1962, Peter Amann offered a definition of revolution as being simply a struggle over political power. He states that a revolution is when two groups struggle for the monopoly of power. When the original government becomes abusive of its power, or unable to manage and maintain a sound society, another group must arise to challenge the power of the ruling party.