I believe Tribes 1 came out before BF, and that had the closest matching
gameplay. Vehicles, aircraft, ground troops, radio commands, chaotic
team-based gameplay, ctf, capture and hold, etc. Tribes was big. It
wasn't WW2, but everything else is essentially the same. Base raping in
Tribes was a whole different game... once they setup in your base, you
pretty much had to sleep on the couch for a while. Memories. ~

.
Tribes was further influenced by Marathon and Terra Nova, but really the
elements that we appreciate in BF started in Tribes.