There's a great song called "The Fighting 69th" by the band Dropkick Murphys, but it's about the original civil war unit.
I had actually wondered for a long time if a kevlar helmet would protect one from a grenade. I wish it was still an unanswered question.
I believe I've heard that song, and it's a good one.
I looked the movie up on Amazon, and it is called The Fighting 69th.
After reading about the movie, it all came back to me: Cagney plays a loud mouth braggart until he is under fire, when he chickens out big time.
I won't say more, or it will spoil the plot, which is a good one, even for an old movie.