Hugo had enlisted the support of fellow Romanticists such as Hector Berlioz and Théophile Gautier[3] to combat the opposition of Classicists who recognised the play as a direct attack on their values.

Hernani is used to describe the magnitude and elegance of Prince Prospero's masquerade in Edgar Allan Poe's short story "The Masque of the Red Death".

[4] Verdi's opera Ernani, with an Italian libretto by Francesco Maria Piave, was based on the play, and first performed in Venice in 1844.

What follows in the ensuing chaos of action prompted the biographer of Hugo, J.P. Houston, to write "... and a résumé [plot synopsis] will necessarily fail, as in the case of Notre-Dame de Paris, to suggest anything like the involution of its details".

[6] In the first scenes Hugo introduces Don Carlos, King of Spain (the future Charles V, Holy Roman Emperor) sneaking into the bedchamber of Doña Sol.

Don Carlos reveals his identity, and asserts that he had come hoping to meet Ruy Gomez to discuss the recent death of Emperor Maximilian, and claims that Hernani is a member of his entourage, thereby allowing everyone to leave peacefully.

As Don Carlos and Doña Sol struggle over a dagger, Hernani arrives with his own sixty men having overtaken the king's three friends.

Hernani admonishes Doña Sol for agreeing to the marriage, but when she reveals that she plans to kill herself on the wedding night, he has a change of heart and encourages her to accept the match.

Hernani reveals his true identity: he is John of Aragon, noble but born in exile; and he abandons his idea of revenge.

Don Carlos is a fictionalized version of the real King Carlos I, later Holy Roman Emperor Charles V. Don Ruy Gomez de Silva, Duke of Pastrana, gets his name from an actual duke by that name, though the fictional version is an old man in 1519 whereas the real de Silva would have been a toddler at this date.