French troops invade the Paris Commune and engage its residents in street fighting. By the close of "Bloody Week", some 20,000 communards have been killed and 38,000 arrested.

The semaine sanglante ("Bloody Week") was a weeklong battle in Paris, from the May 21st, 1871 to May 28th, 1871, during which the French Army recaptured the city from the Paris Commune and the French National Guard. This battle denotes the deadliest period of the 1871 French Civil War and final battle of the Paris Commune.

Following the Treaty of Frankfurt and France's loss in the Franco-Prussian War, efforts to cede territory and pay war indemnities resulted in the French National Guard seizing the city with the French government fleeing Paris and relocating in Versailles. The local governments would eventually unify as the Paris Commune and carry out attacks on Versailles under the leadership of Louis Charles Delescluze. Between May 8th and May 20th, French forces had retaken the territory surrounding Paris and began bombarding the city. On May 21st, French forces entered the city and began retaking territory.

During the week of combat, many Communard (Supporters of the Paris Commune) prisoners were shot by the army immediately after their capture and the movement as a whole was executed en masse following the Paris Commune's surrender. The Commune executed about one hundred hostages, including Georges Darboy, the Archbishop of Paris, and burned many Paris landmarks, including the Tuileries Palace, the Htel de Ville, the Ministry of Justice building, the Cour de Comptes, and the Palace of the Legion of Honor. Fighting continued until May 28th, where Delescluze was killed and the Commune surrendered.

Following the battle, an estimated 10,000 to 20,000 members of the Paris Commune were executed, with the remaining members fleeing into exile. Estimates place the execution count exceeded that of the Reign of Terror and the executions drew considerable criticism from the Parisian population. In 1880, all members of the Commune were pardoned and many returned to public office.

The Paris Commune (French: Commune de Paris, pronounced [kɔ.myn də pa.ʁi]) was a revolutionary government that seized power in Paris, the capital of France, from 18 March to 28 May 1871.

During the Franco-Prussian War of 1870 to 1871, the French National Guard had defended Paris, and working-class radicalism grew among its soldiers. Following the establishment of the Third Republic in September 1870 (under French chief executive Adolphe Thiers from February 1871) and the complete defeat of the French Army by the Germans by March 1871, soldiers of the National Guard seized control of the city on March 18. They killed two French army generals and refused to accept the authority of the Third Republic, instead attempting to establish an independent government.

The Commune governed Paris for two months, establishing policies that tended toward a progressive, anti-religious system of social democracy, including the separation of church and state, self-policing, the remission of rent during the siege, the abolition of child labor, and the right of employees to take over an enterprise deserted by its owner. Feminist, socialist, communist and anarchist currents played important roles in the Commune. However, the various Communards had little more than two months to achieve their respective goals.

The national French Army suppressed the Commune at the end of May during La semaine sanglante ("The Bloody Week") beginning on 21 May 1871. The national forces killed in battle or quickly executed between 10,000 and 15,000 Communards, though some unconfirmed estimates go as high as 20,000. In its final days, the Commune executed the Archbishop of Paris, Georges Darboy, and about one hundred hostages, mostly gendarmes and priests. 43,522 Communards were taken prisoner, including 1,054 women. More than half were quickly released. Fifteen thousand were tried, 13,500 of whom were found guilty. Ninety-five were sentenced to death, 251 to forced labor, and 1,169 to deportation (mostly to New Caledonia). Thousands of other Commune members, including several of the leaders, fled abroad, mostly to England, Belgium and Switzerland. All the prisoners and exiles received pardons in 1880 and could return home, where some resumed political careers.Debates over the policies and outcome of the Commune had significant influence on the ideas of Karl Marx (1818-1883) and Friedrich Engels (1820-1895), who described it as the first example of the dictatorship of the proletariat. Engels wrote: "Of late, the Social-Democratic philistine has once more been filled with wholesome terror at the words: Dictatorship of the Proletariat. Well and good, gentlemen, do you want to know what this dictatorship looks like? Look at the Paris Commune. That was the Dictatorship of the Proletariat."