music/song

The movie begins with a haunting song that is sung by a group of children over images of fields of scrub grass. (Topanga Canyon in 1961 California standing in for a battlefield in 1953 Korea.) Presumably sung in Korean, the word "Isu" seems to be heard. This word is, I think, the Korean name for Jesus, so it is a song about Jesus, sung by children, at the beginning of an anti-war movie. An instrumental version of the tune is also played at the end of the movie. Anybody know what the song is or how it came to be included in the film?