THE Argument in the printed libretto gives a meagre historical background. ‘Arminius, Prince of the Cauchi and Cheruschi, People of Germany, living on the Borders of the Rhine, is well noted in Tacitus’ History, for the memorable Defeat he gave to Three Roman Legions, with the Death of their General QUINTUS VAR US; which affords sufficient Room to extend the Argument. On this Historical Truth, the present Drama is founded, and is attended by other probable Passages, to give the proper Scope to the Musick, and Ornaments to the Representation.’ This tells us nothing about the action of the opera, in which Varus’ defeat and death are reported in three lines of recitative in the last scene. His name was Quintilius, not Quintus.

Act I opens in a Country bordering on the Rhine, with Tents, and other Implements of War. Arminius with his drawn Sword, Tusnelda and German Soldiers. Tusnelda, Arminius’ wife, begs him to fly from the victorious Romans. He is at first reluctant, but yields to her fears that she may be captured. They depart with a duet justifying their action on grounds of love and liberty. Varo enters with Tullio, tribune of the people, and many Roman Soldiers. Tullio reports Arminio's flight; his camp is in Varo's power, but Varo is smitten with love for Tusnelda. Tullio briskly observes that a Roman should control his passions and pursue glory. Varo replies that valour and love are not incompatible; he will demonstrate that the latter strengthens the former. Going off, he meets Segestes with Arminius's Sword, and German Soldiers. Segeste, Prince of the Catti and Tusnelda's father, presents the sword to Varo as symbol of the conquered German Empire. Arminio is led in in Chains, followed by Tusnelda. He denounces Segeste's betrayal of his country and his family. Tusnelda sings an aria about conflicting loyalties and departs. Varo orders Arminio to make his subjection to Rome, but he opts for torture or death; Varo says he is too proud and leaves. Arminio after a defiant aria is led off under guard. Segeste declares that Arminio must be killed if he remains obstinate, since there will be no peace with Rome while he lives.