This melodrama in three acts is one of Giuseppi Verdi's titles that has most been affected by censorship, first of all from the Bourbons in Napoli and then the Popes in Rome, until it was finally premièred at Teatro Apollo in Rome on 17th February 1859. The work, which is based on a real occurrence (the assassination of King Gustave III of Sweden by one of his most loyal ministers, Count Anckarström, during a masked ball), has already given rise to two operas by Daniel Auber ("Gustave III, ou le bal masque") and Saverio Mercadante ("Il reggente"). Verdi finally had to transfer the action from Stockholm to Boston and change the sovereign to governor--the Count of Warwick--but nonetheless managed to create one of the most compact and brilliant compositions of his mature phase, in which amorous passions masterfully overlap political conspiracy.