Setting: 586 B.C.
ACT ONE
In the temple of Solomon in Jerusalem
The Hebrews and the Levites are gathered together in Solomon's temple to lament the fate of the Israelites, who have just been defeated by the Babylonian king Nabucco, who is about to enter the city at the head of his victorious army. The high priest Zaccaria encourages his followers not to abandon hope as they are holding a valuable hostage, Fenena, Nabucco's daughter. Fenena is entrusted to the custody of Ismaele, nephew of the king Sedecia of Jerusalem. Ismaele, however, is in love with Fenena, who had freed him, at a greater personal risk, when he was held prisoner in Babylon. He now intends to return the favour. The two are planning to run away together when Abigaille, whom everyone believes to be Nabucco's first-born daughter enters the temple, carrying a sword in her hand, at the head of a band of Babylonian soldiers who are disguised as Hebrews. In a whisper, Abigaille declares her love to Ismaele and offers freedom to all the Hebrews in return for his love. Ismaele refuses to be blackmailed. In the meantime a crowd of Hebrews, who are being hunted down by Nabucco's soldiers, seek refuge in the temple. Then the king himself appears on the threshold. Zaccaria threatens to kill Fenena if Nabucco and his people dare violate the sacred place. He raises his dagger to Fenena but Ismaele intervenes and saves her from death. Zaccaria condemns Ismaele for being a traitor. Nabucco, embracing his daughter, orders that the temple be put to fire and sword.
ACT TWO
Sacrilege
Scene I
The apartments of the Royal Palace in Babylon
From a document Nabucco had kept secret, Abigaille learns of her true origins; she is not Nabucco's first-born but some slave's daughter. She is disturbed, but perseveres in her plans to wreak vengeance on Fenena, to whom Nabucco has entrusted the throne during his absence fighting the Hebrews. She contemplates having her rival murdered, taking over the throne and spreading the news that Nabucco is dead. She is supported by the high priest of Belo.
Scene II
In another wing of the Royal Palace in Babylon Zaccaria, together with his people, is going to Fenena's apartments to convince her to convert to the Jewish fate. A chorus of Levites is heard cursing Ismaele for having saved Fenena; he is seen as a traitor by everyone. Zaccaria orders the Levites to stop insulting Ismaele, that he is not a traitor as he saved from death a converted woman. Abigaille is about to carry out her plan when Nabucco unexpectedly returns. He grasps the crown and declares himself sole king and God of a people who must adore him for eternity. At these blasphemous words a thunderbolt of lightening strikes beside the terrorised King and he feels the crown being snatched from his head by a supernatural force. A deep silence follows the confusion caused by this mysterious event. Abigaille takes advantage of it to pick up the fallen crown and swears that the "splendour of the people of Belo shall never be extinguished".
ACT THREE
The Phophecy
Scene I
The Hanging gardens in the Royal Palace in Babylon
Abigaille, who has proclaimed herself queen, is seated on the throne to receive the homage of the nobles of the kingdom in the presence of the High Priest. Suddenly Nabucco appears in shabby clothes behaving in a deranged way and Abigaille tricks him into giving the royal seal to ratify the death sentence on all the Hebrew prisoners, including the converted Fenena. Nabucco, realizing the trick too late, protests and orders Abigaille to prostrate herself before him, threatening to reveal the details of her birth. He looks for the birth certificate but - laughing - Abigaille exhibits it in her hands, shows it to him, then tears it to pieces. She consigns the old king to the guards to be imprisoned. Nabucco, in despair, promises Abigaille that he will abdicate the throne in her favour if she grants pardon to Fenena. Abigaille, with a sardonic and scornful smile, refuses to do so.
Scene II
On the banks of the Euphrates
The Hebrews, condemned to hard work, lament their "beautiful and distant motherland" and call on the Lord for help. Zaccaria encourages them with the solemn prophecy that wrathful vengeance is going to descend on Babylon.
ACT FOUR
The Broken Idol
Scene I
Apartments in the Royal Palace of Babylon
Nabucco, waking from a heavy sleep full of nightmares, hears Fenena's name from the street. He runs to the balcony and backs away in terror and desperation on seeing his daughter bound in chains and escorted by soldiers, while all around her echo the cries of "Death!". In vain he tries to leave the palace, only to find himself a prisoner. Then he kneels down in prayer to implore mercy from the God of the Hebrews. The doors immediately open and a band of faithful guards enter he is no longer a poor madman, for they recognize him as the rightful King. With acclamations they unsheathe their swords and follow him to reclaim his crown and free Fenena.
Scene II
In the Hanging Gardens of the Royal Palace in Babylon
Fenena has already been led with other Hebrews to the sacrificial altar erected in the Hanging Gardens, and the High Priest of Belo is about to carry out the sacrificial ceremony, when Nabucco and his followers enter. He orders the overthrow of the simulacrum of the God. The idol, even before being touched, falls to the ground and shatters into pieces. The Jews are liberated and Nabucco exhorts his people to bow before the great God of the Jews, Jehovah. Abigaille, defeated in every way, poisons herself and goes with two of her followers to where the slaughter should have been carried out. Before dying, she asks for her sister's forgiveness and puts the two lovers, Ismaele and Fenena under Nabucco's protection so that the King may allow their marriage and give them his blessing. She dies invoking the God of the Jews
Nabucco: history of a reawakening 
Nabucco was born under a favourable star, considering the fact that everything that could have gone wrong actually contributed instead in a positive sense'. This is how Giuseppe Verdi spoke about his third opera, a veritable leap in the launching of his career which from that moment on met with outstanding success. The history of the success of Nabucco however, was relatively tarnished which is worth elaborating on.
After the success of the first opera by Verdi, Oberto, Conte di S. Bonifacio, performed at the Scala in 1839, the impresario of the Milanese theatre Bartolomeo Merelli had obtained a commitment from Verdi to compose two other operas to be performed in the following seasons. The second opera of the young composer Un giorno di Regno was not as successful as the first, and was performed only once. This is not surprising, if you consider that between 1838 and 1840 Verdi's world was torn apart by the death of his two children and his wife. The unsuccessfulness of his last opera and the pain due to the loss of his loved ones drove the musician to the decision of never writing an opera again. This meant breaking the contract with Merelli who hadn't lost his faith in Verdi and who confirmed this faith to him.
It was really due to Merelli that the composer started to write new operas. One winter evening the two of them met up on the street and the impresario entrusted him with the manuscript of a new libretto by Temistocle Solera, which had been refused by the German composer Nicolai. In this way Verdi found himself again in the possession of a libretto which he had no intention of reading and consequently, as soon as he arrived home, he threw it on the table. Following this jest, the manuscript opened and the composer read a verse which awakened his curiosity: 'Va' Pensiero sull'ali dorate'. He began to read the successive verses and was so fascinated that he spent the night reading the libretto, reaching the point where he almost knew the text off by heart.
The event, however, did not dissuade him from his decision never to write music again. In fact, he went back to Merelli to return the manuscript to him, but the impresario didn't want to listen to excuses and forced him to keep the libretto, urging him to put it to music.
At that stage destiny had taken its course, and the verses of Solera had already entered into Verdi's heart. Day after day he found the strength to compose the notes: in the autumn of 1841 the opera Nabucco was complete. The irony was that it was actually Verdi then who went looking for Merelli, to ask him to insert the new opera in the poster for the carnival-lent season of 1841.
The impresario appeared to be hesitant, however, as he had already programmed three unpublished operas by established authors for that period. To insert the opera of a debutant involved a risk for everyone and Merelli warmly advised Verdi to wait until the spring. Furthermore, the theatre had had to sustain a lot of expenses for the other operas: for the scenes and costumes of Nabucco they would have had to use the existing material from the store room. The young musician didn't want to give in however, and continued to insist, succeeding finally in obtaining the long-awaited date. The opera was fixed for the beginning of March.
Various important artists were in the cast, such as the baritone Giorgio Ronconi, who played the role of Nabucco and the soprano Giuseppina Strepponi (Verdi's future wife) who played the role of Abigaille. On March 9th 1842, after only twelve days of rehearsals, the Milanese public attended the première of the opera and was completely captivated.
Despite the universal fact that it was Va' Pensiero which deserved the encore, in reality it was the Immenso Jehovah which obtained the most generous applause. The enthusiasm of the spectators grew at every performance, so much so that the opera was performed seventy five times before the end of the year. A success for Verdi without precedent and which revealed his true talent in all its glory. With the passing of time Va' Pensiero became the most famous air of Nabucco. The Jewish population was, in fact, similar to the people of Lombardo-Veneto who were obliged to endure the Austrian domination, and the tune for the freedom of the slaves in Babylon was the tune of the oppressed Italians. Verdi was a veritable point of reference for the patriotic Italians who suggested that Va' Pensiero become the national anthem. This proposal was never carried out, but the fame of Nabucco was linked to the air of the third act, which is sung by the great chorus.
From Nabucco onwards the young man from Bussetto moved towards the career which allowed him to become one of the most admired and loved musicians of his era.