I have the first two on GBA, and although I've never actually seen any others, apparently there's quite a series. Does anybody know which of these came out (and whether US or import)?

CT Special Forces 3: Navy Ops (gba)
CT Special Forces (psx)
CT Special Forces: Back to Hell (psx)
CT Special Forces: Fire for Effect (ps2)
Special Forces: Nemesis Strike (xbox)
Special Forces: Nemesis Strike (PC)

Navy Ops, I haven't been able to find any confirmation of a US release (only Europe), but they gave it a different subtitle for the US; it would be odd that they would bother re-titling it and then not release it. I didn't see CT Special Forces on Dangerboy's list, so I'm thinking it probably only came out in Europe, except GameFAQs actually lists it with a US release date (not that they're always accurate or anything, but still).