"like beads, on a great iron chain"

   An occasional practice of ancient civilisations, the use of slaves or condemned criminals to man war galleys was revived by, and became increasingly common in, certain medieval societies.  Even in times of peace many rulers saw the profit in diverting as many prisoners as possible into the lowest form of naval service, which for most was no more than a delayed death sentence anyway.  Cervantes himself not only fought in naval battles during which both sides used prisoners of war as galley slaves, but went on to spend five years in the sort of 'bagnio' prison reserved for them (See note to page 359).