What language was this movie originally shot in?

I believe it was a joint Italian/French production, but I think lines may have been read in the actor's native language, then dubbed for the particular market, like the American actors in Sergio Leone's films. I know Delon spoke English, so he might have been speaking English or French. Baker was definitely speaking his lines in English.

Wondered that myself at times. A lot of times there was obvious dubbing, especially where Garcia and Brother Francisco were concerned.