While Prussia and Austria regrouped and enlisted the support of Great Britain and Spain, the Convention started to worry that foreign threats and internal chaos would quickly lead to its demise, so it threw out the constitution and created the Committee of Public Safety, an all-powerful enforcer of the revolution and murderer of anyone suspected of antirevolutionary tendencies. Led by Maximilien Robespierre and the Jacobins, the Committee of Public Safety certainly wasn't a committee of personal safety, since it was responsible for the beheading of tens of thousands of French citizens. Even though the Committee was successful at controlling the anarchy and at building a strong national military to defend France against an increasing number of invading countries, after two years the French had enough of Robespierre's witch hunt and put his own head on the guillotine. France then quickly reorganized itself again, wrote a new constitution in 1795, and established a new five-man government called the Directory.
The Height of Napoleon's Empire
While the Directory was not so great at implementing a strong domestic policy, the five-man combo was good at building up the military. One of its star military leaders was a teenager named Napoleon Bonaparte, who was a general by age 24. After military successes on behalf of the Directory, Napoleon returned to France and used his reputation and immense popularity to overthrow the Directory in 1799. He legitimized his actions by putting them before a popular vote, and once affirmed, he declared himself the First Consul under the new constitution (if you're counting, that makes four constitutions since the Revolution began).
Domestically, Napoleon initiated many reforms in agriculture, infrastructure, and public education. He also normalized relations with the church and restored a degree of tolerance and stability. Most importantly, his Napoleonic Codes (1804) recognized the equality of French citizens (meaning men) and institutionalized some of the Enlightenment ideas that had served as the original inspiration for many of the revolutionaries. At the same time, the code was also extremely paternalistic, based in part on ancient Roman law. The rights of women and children were severely limited under the code, for example. Still, the code was a huge step forward in the recognition of some basic rights and in the establishment of rules of law. The code has since been significantly modified to reflect more modern sensibilities, but it is still in effect today, and has served as the model for many other national codes, especially in Europe.
But Napoleon's biggest impact was external, not internal. In a stunning effort to spread France's glory throughout Europe and the Americas, Napoleon not only fended off foreign aggressors, but also made France an aggressor itself. Napoleon's troops conquered Austria, Prussia, Spain, Portugal, and the kingdoms within Italy. He dissolved the Holy Roman Empire, which was on its last legs anyway, and reorganized it into a confederacy of German states. In 1804, he crowned himself emperor of this huge new empire, fancying himself the new Charlemagne. By 1810, the empire was at its peak, but it didn't stay there for long. France lacked the resources to control a far-flung empire, and conflicts with a powerful Britain cost it dearly. Nationalistic uprisings, such as unrest in Italy and fierce guerilla warfare in Spain and Portugal, undermined his power.
In 1812, Napoleon's greed got the better of him. He attacked the vast lands of Russia, but was baited into going all the way to Moscow, which the Russians then set aflame, preventing Napoleon from adequately housing his troops there. As winter set in and with no place to go, the troops had to trudge back to France, and were attacked all along the way. Short on supplies, the retreat turned into a disaster. The army was decimated and the once great emperor was forced into exile.
The leaders of the countries that had overthrown Napoleon met in Vienna to decide how to restore order (and their own power) in Europe. The principal members of the coalition against Napoleon were Prince von Metternich of Austria, Alexander I of Russia, and the Duke of Wellington of Britain. At first, disagreements among them prevented much progress. Hearing this, Napoleon returned from exile and attempted to regain power. His enemies, of course, rallied. At Waterloo in 1813, the allies united against their common threat. Defeating Napoleon decisively, they sent him to permanent exile on the island of St. Helena, where he later died. The allies eventually came to an agreement, in a meeting known as the Congress of Vienna, over what to do with France and its inflated territories.