The Regency of Algiers was no minor power. An Ottoman-backed state that had achieved de facto independence in 1710, it governed through an elected ruler called the Dey and a parliament called the Divan. Its corsairs had terrorized Mediterranean shipping for centuries, provoking wars with the United States, bombardments by the British and Dutch, and a failed Spanish invasion in 1775. But by 1830, the Regency was weakened by internal instability and declining revenues. Hussein Dey mobilized his forces as the French fleet approached, levying tribal warriors from across the Beyliks of Constantine, Oran, and Titteri, along with Kabyle fighters from the mountains. Estimates of his army range from 25,000 to 50,000 men, though only about 7,000 were professional janissary soldiers.

The French landed at the Sidi Ferruch peninsula, twenty-five kilometers west of Algiers, on June 14. Five days later, the Algerian army attacked the beachhead at the Battle of Staoueli and was routed, its camp captured along with weapons, food, and livestock. A second engagement at Sidi Khalef on June 24 ended in another Algerian defeat; among the French dead was Amedee de Bourmont, one of the commander-in-chief's four sons. The decisive moment came at the Bordj Moulay Hassan fortress -- which the French nicknamed "Fort de l'Empereur" after Charles V, whose own assault on Algiers had failed in 1541. On July 4, after hours of bombardment, the garrison of 800 janissaries and 1,200 Moors, having fought until every merlon was destroyed, blew up the fortress rather than surrender. Half the garrison died. With the fortress gone, Algiers lay exposed.

Hussein Dey's envoys first proposed a French withdrawal in exchange for an apology and war reparations. The French refused. The envoys then offered to bring the Dey's head. The French declined that too. Marshal de Bourmont's terms were absolute: the city, the fleet, the treasury, and the departure of the Turkish ruling class. In return, he promised the inhabitants' homes would not be pillaged. Hussein agreed. French troops entered Algiers on July 5 at noon. The Dey and his family boarded a frigate bound for Naples. Within a month, 43 million francs in gold and silver from the Regency's treasury were shipped to France -- not counting what soldiers pocketed for themselves, a scandal that embarrassed Paris. Alexis de Tocqueville later compared France's situation to a hypothetical Chinese invasion of France: a conqueror who had burned all the archives, expelled the entire ruling class, and now found himself governing a country whose language, laws, religion, and customs he did not understand.

The fall of Algiers was swift. The conquest of Algeria was not. What the French expected to be a punitive expedition became a colonization project that took more than forty-five years to complete. Resistance figures like Emir Abdelkader waged prolonged campaigns that tied down French forces for decades. The invasion destroyed libraries, land surveys, and the administrative structures that had governed Algerian society. In 1848, the conquered territories were reorganized into three French departements, legally incorporating Algeria into France -- a status that would endure until the violent end of the Algerian War in 1962. Meanwhile, Charles X, who had launched the invasion partly to shore up his faltering grip on power, was overthrown in the July Revolution just weeks after Algiers fell. The conquest he ordered to save his throne outlived his reign by 132 years.