What situations exist within a country that drive its people to revolution?

Revolutions are very complex, and arise for a number of different reasons. Let us look at a few of them, with some examples.

One condition that often leads to revolution is the existence of a class of people that feels disfranchised or shut out from full political or social participation. A good example of this would be the bourgeoisie, the members of the Third Estate in pre-Revolutionary France. They were mostly comfortable, educated merchants and...

Revolutions are very complex, and arise for a number of different reasons. Let us look at a few of them, with some examples.

One condition that often leads to revolution is the existence of a class of people that feels disfranchised or shut out from full political or social participation. A good example of this would be the bourgeoisie, the members of the Third Estate in pre-Revolutionary France. They were mostly comfortable, educated merchants and businessmen who felt that their social mobility was restrained by the old order in France, which retained certain privileges for the nobility and the clergy. Another example of this condition is the gens de couleur libre in Saint-Domingue. These people were mostly of mixed race, owning many slaves and controlling considerable wealth, but they were not allowed to vote or participate in the island's society in meaningful ways. They were the initial leaders of what would become the Haitian Revolution. Some people argue that the leaders of the American Revolution felt the same way about their place in the British Empire.

Another condition that leads to revolution is a nation's participation in a war. When things go bad, sometimes a revolution can ensue. The Russian Revolution is the classic example of this. Russian participation in World War I had been disastrous, leading to costly and humiliating defeats as well as severe shortages on the home front. This helped lead to the Russian Revolution, and the failure of the Provisional Government to remove the nation from the war after the first wave of the revolution helped lead to the Bolshevik Revolution, whose leaders promised the Russian people "peace, land, and bread."

Finally, nationalism can be a powerful force contributing to revolution. We can see it at work in the revolutions that spread throughout Europe in the early to mid nineteenth century. People came to feel nationalistic bonds with other peoples within their nation, and they resented being controlled by what they had come to see as foreign empires. Greek revolutionaries sought independence from the Ottoman Empire, Belgium from France, Hungary from Austria, and many others. Other revolutionaries, like in Italy and the German states, sought to unify their "nations," barely conceived of before then. 

All of these conditions can help contribute to revolutions, but there are many more. While comparing revolutions is a rich field of historical study, ultimately each revolution is unique.