Act I: The Israelites have been under the rule of the neighbouring Ammonites for eighteen years and have adopted many of their ways and worship of their gods. They face the loss of their country and their religious identity unless they rebel, as Zebul tells them (Accompanied recitative: It must be so). Zebul advises them to recall his half-brother Jephtha from exile so he can lead them to freedom and to repent of their worship of the Ammonites' idols (Air: Pour forth no more unheeded pray'rs). The Israelites vow to stop their sacrifices to the Ammonite gods Moloch ( a god associated with child sacrifice) and Chemosh and thenceforth to worship Jehovah only(Chorus: No more to Ammon's god and king). Jephtha, trusting in his own virtue, agrees to lead the Israelites in battle against their enemies on condition that if he is victorious he will be their leader in peacetime afterwards (Air: Virtue my soul shall still embrace). His wife Storgé supports his mission to win freedom for their country but will miss him sorely while he is away (Air: In gentle murmurs will I mourn). Iphis, only child of Jephtha and Storgé, is asked by her sweetheart Hamor to marry him soon (Air: Dull delay, in piercing anguish) but she tells him to prove himself worthy of her by fighting valiantly under her father's command first (Air: Take the heart you fondly gave). He agrees to this and the pair look forward to a happy future together after their country has achieved its freedom (Duet: These labours past, how happy we!) Jephtha, alone, vows to the Almighty that if he is allowed to win victory over Israel's enemies, he will sacrifice to God the first living thing he sees upon his return after the battle(Accompanied recitative: What mean these doubtful fancies of the brain?) The Israelites implore divine assistance (Chorus: O God, behold our sore distress). Jephtha's wife Storgé is unaware of her husband's rash vow but she is experiencing presentiments of tragedy (Air: Scenes of horror, scenes of woe). She explains to her daughter that she has had dreams of danger to Iphis, but Iphis attempts to dismiss her mother's nightmares as meaningless (Air: The smiling dawn of happy days). The Israelites have sent an embassy to the king of the Ammonites offering peace terms, but it has been rejected. Therefore, Jephtha orders the Israelites to prepare for war and they express their confidence that God will aid them (Chorus: When His loud voice in thunder spoke).