Theme song from a 1964 movie, "Advance to the Rear," released by MGM. It's a comedy western set during the Civil War and stars Glenn Ford and Stella Stevens. As Uncle DaveO says, it's very much unlike a traditional song and was surely written for the movie. (Movie is adapted from a Jack Schaefer novel that was published as "Company of Cowards," and no doubt that was the working title of the film.)

The credits should give the composer's name, but the IMDb page doesn't give the full credits for the film. A comment on the page says that the music was written by Randy Sparks. The song is sung over the intro credits.

This film plays from time to time on Turner Classic Movies but I don't know if it is available on VHS or DVD.