At that point, Sulpice returns, surprising the young couple, who leave.
The Marquise arrives with Hortensius, initially afraid of the soldier, but is calmed by him.
She quickly tells him that he must gain the approval of her "fathers": the soldiers of the Regiment, who found her on the battlefield as an abandoned baby, and adopted her.
He proclaims his love for her (aria, then love duet with Marie: Depuis l'instant ou, dans mes bras / "Ever since that moment when you fell and / I caught you, all trembling in my arms..."), and then the couple express their love for each other.
All toast Tonio, who pledges allegiance to France, and Marie is encouraged to sing the regimental song: (aria: Chacun le sait, chacun le dit / "Everyone knows it, everyone says it").
Sulpice leads the soldiers off, taking Tonio with them, but he runs back to join her.
La fille du régiment (The Daughter of the Regiment) is an opéra comique in two acts by Gaetano Donizetti, set to a French libretto by Jules-Henri Vernoy de Saint-Georges and Jean-François Bayard.
It was first performed on 11 February 1840 by the Paris Opéra-Comique at the Salle de la Bourse.
As the French can be seen to be moving away, all express their relief.
Suddenly, and provoking the fear of the remaining women who scatter, Sergeant Sulpice of the Twenty-First Regiment of the French army [in the Italian version it is the Eleventh] arrives and assures everyone that the regiment will restore order. Then, as he questions her about a young man she has been seen with, she identifies him as Tonio, a Tyrolean [in the Italian version: Swiss].