This is one of my childhood games. Used to play it all the time, AI in there posed quite a challenge despite everything. With friends we'd compare our favourite weapons, which mission was the hardest (third mission, if I remember right, Peru, in the first campaign, was hell for me).
What's more important? It had specialities, classes if you will. Each time you got shot, you could come back as a different specialist.
This game is nowhere to be found. But the community for it is living as far as I know, even if small. It's a not-so-popular title, somewhere between SWAT and Counter strike with how you can communicate with teammates with shortcuts.
It deserves a chance now, when we need such titles in the age of modern releases.