is that a "war game"? he wants a "war game" and he isn't sure civ4 is what he wants. he'll probably quit any game after 2 minutes b/c all he's so green, but i want to give him the best chance to enjoy something. he can't handle rts, but thematically, what he wants is company of heroes or a civil war strategy game.
for Civil War the choices are easy in terms of wargames-Gary Grigsby's War Between the States, AGEOD's American Civil War, and the older Take Command: Second Manassas. All three are pretty advanced games and not made for novice gamers and would be unsuitable for new players unless they came from tabletop wargaming backgrounds. For WW2 there are a ton of games, ranging from the massive scope of Hearts of Iron and War in the Pacific to small-scale operational stuff like Kharkov: Disaster on the Donets, and again most of those are essentially not approachable from the novice gamer.
Honestly, perhaps the best thing would be something like the now-abandonware Axis and Allies: Iron Blitz - total beer and pretzels pivoted around a familiar conflict. However, giving the gift of grey-area downloads isn't much of a gift.

That being said, one very good choice along those lines might be Gary Grigsby's World at War , which is a deep game but has a pretty decent interface and is pretty straightforward.
If he just wants something to pick up and play and blow something up, you could always get him DEFCON, which is a "war" game that is fun and plays pretty quick, and runs on about anything.