Oh yeah, Battlefield from the album A Night at the Opera, which appeared in Robot Unicorn Attack: Heavy Metal.
For me, it was the other way around, I was already into BG when I found out about the flash game, but I hadn't listened to that song yet.>>2826
I tried giving Civil War a listen, didn't like it sadly. Rikard Sundén turned out to be a pedo :(
After Carolus Rex (which was the last album with the original lineup IIRC) Sabaton released Heroes. It's a solid album IMO, I bought it (as well as Carolus Rex). Night Witches might be one of my favorite songs by them.