Hmm, I don't think so; it may be a commando infiltration game but it's pretty much a linear FPS that doesn't let you choose a different approach for your objectives.

Well, thanks for all the suggestions! They all fit the description somehow, but it just showed me again that apparently games that are a bit closer to the likes of IGI, with seperate missions instead of open worlds, and probably not all that complicated mechanics, mainly focused on shooting, aren't very plentiful. But, this firstly sparked my interest in Ghost Recon, which I guess I will give a try a bit sooner than I thought :)

Sad news indeed. I had planned to play the game at some point in the future (many FPS games already in my backlog), but since I don't like to buy games I'm not going to play in the short term (particularly on Steam), and, well, I generally don't like buying on Steam anyway, I had always postponed the purchase. If I had known they were going to remove it, in the end I would have bought it, especially whenever I saw it popping up during sales for the price of an espresso, or less. Well, let's hope it comes back to Steam, or, even better, gets released on GOG (it's a Polish game! But the wishlist entry so far has just 107 votes...)