The scene on the railroad tracks is a reference to the final adventure in Mexico of beatnik figure Neal Cassady, Jack Kerouac's inspiration for Dean Moriarty in "On the Road". Author Robert Stone had traveled with Cassady and Ken Kesey's Merry Pranksters. Furthermore, Nick Nolte was in the midst of extensive research on Cassady for his portrayal in the film Heart Beat (1980).
The producers were lukewarm about casting Nick Nolte at first, instead preferring the more bankable Kris Kristofferson. Director Karel Reisz fought to get Nolte on board, having been impressed by seeing him in action on Rich Man, Poor Man (1976).
Nick Nolte says in his biography that this movie was a box office failure, but he did not care because he was very proud of his work. And the thanked Karel Reisz for his work.
It is often believed that film's title was changed from "Dog Soldiers" so as not to be confused with the similarly titled novel of The Dogs of War (1980) by Frederick Forsyth which got made and released as a movie a couple of years later. However, the producers changed the title when they acquired the rights to use the song "Who'll Stop the Rain". The film was still released though as "Dog Soldiers" in a number of foreign territories.