It replaced the original song sung by Maria and Captain Georg von Trapp called "An Ordinary Couple".
[1] It was first recorded by Julie Andrews and playback singer Bill Lee (dubbing over the voice of actor Christopher Plummer)[2] for the film's soundtrack.
In The Making of The Sound of Music by Max Wilk, Wilk stated that when Robert Wise and Saul Chaplin discussed replacing "An Ordinary Couple" with Rodgers, he automatically agreed to the idea and admitted he and lyricist Oscar Hammerstein II had been talking of replacing the song but Hammerstein had been too ill to do so.
The magazine asserted that on a literal level, it is a song about redemption between Maria's past (and the real woman's difficult childhood and suspicion of the Church) contrasted with the Captain's "loving response to her."
However, the article continued that the song covertly provides a "rationale for America's response to Salzburg" in the wake of Nazism—that Europe essentially had a good heart.