Barbary Coast in the context of "Second Barbary War"

The history of slavery in the Muslim world was throughout the history of Islam with slaves serving in various social and economic roles, from powerful emirs to harshly treated manual laborers. Slaves were widely in labour in irrigation, mining, and animal husbandry, but most commonly as soldiers, guards, domestic workers. The use of slaves for hard physical labor early on in Muslim history led to several destructive slave revolts, the most notable being the Zanj Rebellion of 869–883. Many rulers also used slaves in the military and administration to such an extent that slaves could seize power, as did the Mamluks.

Most slaves were imported from outside the Muslim world. Slavery in the Muslim world did not have a racial foundation in principle, although this was not always the case in practice. The Arab slave trade was most active in West Asia, North Africa (Trans-Saharan slave trade), and Southeast Africa (Red Sea slave trade and Indian Ocean slave trade), and rough estimates place the number of Africans enslaved in the twelve centuries prior to the 20th century at between six million to ten million. The Ottoman slave trade came from raids into eastern and central Europe and the Caucasus connected to the Crimean slave trade, while slave traders from the Barbary Coast raided the Mediterranean coasts of Europe and as far afield as the British Isles and Iceland.

The Barbary corsairs, Barbary pirates, Ottoman corsairs, or naval mujahideen (in Muslim sources) were mainly Muslim corsairs and privateers who operated from the North African coast, known in Europe as the Barbary Coast, in reference to the Berbers. Slaves in Barbary could be of many ethnicities, and of many different religions, such as Christian, Jewish, or Muslim. Their predation extended throughout the Mediterranean, south along West Africa's Atlantic seaboard and into the North Atlantic as far north as Iceland, but they primarily operated in the western Mediterranean. In addition to seizing merchant ships, they engaged in razzias, raids on European coastal towns and villages, mainly in Italy, France, Spain, and Portugal, but also in Britain and Ireland, and Iceland (commemorated as the Turkish Abductions).

While such raids began after the Muslim conquest of the Iberian Peninsula in the 710s, the terms "Barbary pirates" and "Barbary corsairs" are normally applied to the raiders active from the 16th century onwards, when the frequency and range of the slavers' attacks increased. In that period, Algiers, Tunis and Tripoli came under the sovereignty of the Ottoman Empire, either as directly administered provinces or as autonomous dependencies known as the Barbary states. Similar raids were undertaken from Salé (see Salé Rovers) and other ports in Morocco.

The Regency of Algiers was an early modern semi-independent Ottoman province and nominal vassal state on the Barbary Coast of North Africa from 1516 to 1830. Founded by the privateer brothers Aruj and Hayreddin Reis (also known as the Barbarossa brothers), the Regency succeeded the Kingdom of Tlemcen as a formidable base that waged maritime holy war (Jihad) on European Christian powers. It was ruled by elected regents under a stratocracy led by Janissaries and corsairs. Despite its pirate reputation in Europe, Algiers maintained long-standing diplomatic ties with European states and was a recognized Mediterranean power.

The Regency emerged in the 16th-century Ottoman–Habsburg wars. As self-proclaimed ghazis gaining popular support and legitimacy from the religious leaders at the expense of hostile local emirs, the Barbarossa brothers and their successors carved a unique corsair state that drew revenue and political power from its naval warfare against Habsburg Spain. In the 17th century, when the wars between Spain and the Ottoman Empire, Kingdom of France, Kingdom of England and Dutch Republic ended, Barbary corsairs started capturing merchant ships and their crews and goods from these states. When the Ottomans could not prevent these attacks, European powers negotiated directly with Algiers and also took military action against it. This policy would emancipate Algiers from the Ottomans.

The Barbary slave trade involved the capture of Europeans and selling them at slave markets in the largely independent Ottoman Barbary states of North Africa. Europeans were captured by Barbary corsairs in slave raids on ships and by raids on coastal towns from Italy to Ireland, coasts of Spain and Portugal, as far north as Iceland and into the Eastern Mediterranean.

The Ottoman Eastern Mediterranean was the scene of intense piracy. As late as the 18th century, piracy continued to be a "consistent threat to maritime traffic in the Aegean".