Poliuto and Les martyrs. Although La fille du régiment had its first performance at the Opéra-Comique in February 1840 and Les martyrs would not be performed until the following April, the roots of the latter work go back to 1838. Donizetti composed Poliuto before his departure from Naples, where it had advanced as far as preliminary rehearsals before the king's prohibition forestalled its actual performance. Donizetti wrote Poliuto, like L'assedio di Calais, with more than half an eye to its potential for being recast as a French grand opera. He expanded and altered the score into Les martyrs in 1839 in Paris. Since about eighty percent of the French version in four acts is made up of Poliuto, and since the three-act Italian score enjoys the greater currency, it makes sense to discuss Poliuto before examining the alterations and change of emphasis it later underwent.

The literary source of Poliuto is Corneille's tragédie chrétienne, Polyeucte (1641–2). Cammarano's libretto converts Corneille's spiritual drama, with its carefully observed unities, into a Romantic melodrama, adding the motive of Poliuto's jealousy (which does not occur in the French original) to turn the action, at least in part, into a stock tenor–soprano–baritone triangle. Donizetti may have played some part in this emendation of Corneille, for he had complained in a letter to Toto Vasselli, speaking of Poliuto: ‘there is little love interest in it’.