There have been many revolutions across history. Some revolutions are peaceful, and many can be positive. The Industrial Revolution, for example, transformed manufacturing, and completely changed transport with the invention of combustion engines.
Many more revolutions, however, are violent. This is especially (but not always) true if revolutions are trying to change the politics of a country. Perhaps the most famous of these political revolutions was the French Revolution in 1789.
Although nobody could have known it at the time, the French Revolution marked the start of a series of events which would draw the nations of Europe, and their empires, into the first truly global war. Between 1792 and 1815, France was almost constantly at war, fighting on almost every continent and ocean in the world. So large was the scale of death and destruction that, until World War One a century later, the French Revolutionary and Napoleonic Wars was known as the 'Great War'.
However, the initial aims of the French Revolution were not to spark a global conflict, or dominate the world. Instead they were focused inwards, hoping to reform huge social injustices that affected the country. In 1788, 95% of the population of France could not vote. The King ruled with absolute and unshared power over his people, whilst the bulk of taxation fell on those least able to afford it, as the nobles used a variety of imaginative reasons to avoid paying tax.
There were many positive legacies of the revolution. Perhaps the biggest of these is the Declaration of the Rights of Man. This document was so influential that almost half of the UN's Universal Declaration of Human Rights is based on it. The Revolution may have brought about war, but its founding principle was one of peace.
King Louis xvi
The Revolution initially tried to create a Constitutional Monarchy (a system of government where the ruler's power is limited, and their actions are restricted by an elected group of people). Over time though, the situation escalated out of hand. France descended into war, as the governments of other countries grew fearful of the ideas of the revolution, and in 1793 King Louis was executed for treason.
Over the next six years, France defeated the armies of Europe in a series of remarkable victories, expanding its borders to the River Rhine, and establishing control over Northern Italy with the help of a dynamic young general called Napoleon Bonaparte.
At home, a civil war erupted after the execution of the King. Although opposition to the revolution inside France was swiftly crushed, a wave of executions using the guillotine followed in which any who was believed to be undermining the revolution was executed. This became known as the 'Reign of Terror' or 'Great Terror' (October 1793 - July 1794), and was largely caused by Maximilien Robespierre, and his associates, who led the French government at the time. Estimates of the number of people killed range from the thousands to tens of thousands. Ultimately the Terror was only brought to an end by the arrest of Robespierre, who was himself guillotined.
The new style of government in France proved too unstable, as there was little agreement on a new constitution (set of rules on how the government should work). Napoleon, who at the time was fighting in Egypt, returned to France in the hope of exploiting this political crisis. In November 1799 he took power in a coup, establishing himself as the 'First Consul' and proclaiming 'the Revolution is established on the principles with which it began. It is over'. During the next four years he ruled as leader of France in all but name, until he crowned himself Emperor of France in 1804. The revolution truly was over.