Complex sentence: Reivers served as mercenaries, or were forced to serve in English and Scots armies in the Low Countries and in Ireland; such service was often handed down as a penalty in lieu of that of death upon their families.
Split into simpler sentences: Reivers served as mercenaries, or were forced to serve in English and Scots armies in the Low Countries and in Ireland. Such service was often handed down as a penalty in lieu of that of death upon their families.