Diorama of convicts on galley benches at the Museu Maritim, Barcelona.
Slaves were used as oarsmen by all the main galley powers of the Mediterranean. The Ottomans preferred free oarsmen because they doubled as marines once a boarding action began. Often, these were Christian mercenaries from Greece and the Balkans who dropped oars and took up weapons in a fight. Most Ottoman ships also had a minority of Christian slaves chained to the oars. Venice also preferred freemen at the oars of its galleys for tactical reasons: it was rich but had a tiny population relative to its enemies, which forced it to hire mercenaries as oarsmen who could double as marines. Venice used a few slaves, usually criminals or prisoners of war. The Barbary Corsairs used all freemen in galliot raids, in which on-deck combat power was the primary concern. In fleet actions they used Christian slaves at the oars. They captured most of these poor fellows in raids on Sicily, Italy, and Spain, but sometimes as far afield as England, Wales, and Ireland. Most captured Christians preferred the hard life of a pirate to the harder life of a slave. Some were skilled seamen and were allowed to leave the oars if they converted to Islam. Some of the most dangerous Muslim captains were therefore Englishmen. Among the Mediterranean powers Spain was the most reliant on slave oarsmen. This held down costs, a concern for a country overcommitted on many fronts against too many enemies in the 16th–17th centuries. Slaves on Spanish galleys were a mix of North African and Ottoman prisoners of war, and religious convicts (conversos and moriscos) sentenced to the oars after falling afoul of the Inquisition. Other Italian powers, including the warrior popes of the Papal States, kept small fleets of galleys rowed by a mix of slaves and mercenaries. The Scots and Irish used galleys that descended from Viking longships. These were rowed by allwarrior crews who took part in raids, not by slaves. The French used coerced oarsmen in coastal galleys into the 18th century, but these were convicts condemned to prison galleys, not slaves per se.
