In each level of Stealth Combat, you control a vehicle, ranging from an armed jeep to a Star Wars-like walker. Often (but not always) you have a variety of subordinate vehicles you can issue orders to. Each mission has a series of objectives--and generally, the other side has enough firepower to wipe out your entire force if you just charge in firing blindly. Which is where the "stealth" aspect comes in; this isn't quite Thief for vehicles--combat is often necessary--but succeeding typically requires a degree of finesse as well as mastery of the combat UI.
Combat is of the 'arcade shooter' style; while there is a good sense of controlling a vehicle over terrain, the emphasis is definitely not on simulation of vehicle characteristics and different types of armaments. But of course, in 2030, who knows what sort of equipment different armies will have.
The backstory is that two superpowers are on the brink of war, and as an elite commander from one side, you have to find out what's going on, and avert global thermonuclear conflict. There are two campaigns, each one from one side's viewpoint--and as it happens, the tension is created by a third party that hopes to benefit, and by the end of the campaign, you're working with the "opposition." (We won't call this "the game equivalent of Rashomon", but it is interesting to come at the same story from two different viewpoints).
The superpowers, by the way are the "Economic and Military Alliance," which seems to be a sort of super-European Union--and "Great Asia." This is also a nice change from the usual crap; no Amurrican chest-pounding triumphalism here. Maybe that's why the US publishers passed.
The production values of Stealth Combat are pretty decent; this was an A-level (if not triple-A) title in its year of publication (2001), and the graphics hold up pretty well today. Despite its limited distribution outside Europe, we're suprised it hasn't received more attention; it's well conceived, professionally executed, tense, and has a pretty good story arc.
If the concept and the style appeal to you--well, you really can't do better at its current price (which is $10 for the full game).