Rowers
Contrary to the popular image of rowers chained to the oars, conveyed by movies such as Ben Hur, there is no evidence that ancient navies ever made use of condemned criminals or slaves as oarsmen, with the possible exception of Ptolemaic Egypt.
The literary evidence indicates that Greek and Roman navies generally preferred to rely on freemen to man their galleys. Slaves were put at the oars only in exceptional circumstances. In some cases, these people were given freedom thereafter, while in others they began their service aboard as free men.
In the Middle Ages, galleys continued to be rowed predominantly by free men, either conscripted or hired. This had the advantage that these men could be armed, thus the proportion of fighting complement to motive power remained high. By the 16th century, this was becoming harder to sustain economically and there was an increase in the use of convicts and slaves. This led to a drop in efficiency, as more soldiers needed to be carried, and a change in rowing design to accommodate less skilled oarsmen.
In early modern times, it became the custom among the Mediterranean powers to sentence condemned criminals to row in the war-galleys of the state, initially only in time of war. Galley-slaves lived in very unhealthy conditions, and many died even if sentenced only for a few years - and provided they escaped shipwreck and death in battle in the first place.
Prisoners of war were often used as galley-slaves. Several well-known historical figures served time as galley slaves after being captured by the enemy, including the Ottoman corsair and admiral Turgut Reis and the Maltese Grand Master Jean Parisot de la Valette.
Read more about this topic: Galley