Use the cigarettes to lure away the guards

It is possible as I've completed the two games myself, albeit only on the easy difficulty which still isn't that easy :P
Use the Green Beret's decoy and lure a single guard away, then when he turns back, hopefully you've lured him out of sight of the others.
As the reviews say, persistence is key.
EDIT: Yes, forgot about the cigarettes too, they help.

I was never told to use the cigs :\

Using cigarettes make this game way too easy. :(

Well, where to start....
You do understand the premise of these games yes? Their entire point is that you have to be strategic and tactical to finish the missions with your squad intact. The game makes you think, or at least attempts to, requiring planning and timing to ensure you don't end up raising an alarm or ending up dead. You stated that "It makes it hard to plan strategies", well thats on purpose, thats the fun off this game, it actually a challenge! It was never designed so that you could run around like a lunatic with guns blazing and actually get anywhere. I've played missons over and over again using many different approaches, some of which were good and some were bad. But I didn't resent the game for making me try harder. Actually I was quite impressed by it :)
The idea that you're suprised that each corner is guarded intrigues me, and tbh makes me a wonder how you would station the guards to stop the commandos getting in.
Many games that have been released recently lack major challenge and go more for instant gratification. Which I'm not suggesting is neccessarily a bad thing, just a different trend than what this game is going for. I'd suggest you may rather something a little more instant action, like company of heros, TF2 maybe or something a little more casual? Thats not meant in a derogoratory way, I'm a big fan of both those games and play them regularly, and I'm not adverse to a round of peggle either :P
Its a shame that you've seemed to have appreciated the concept as a child, but now feel its making you work too hard. Going on what you've said, I really don't think this game is the one for you any more which is a shame. at what it does it really is still one of the best.

Don't get me wrong i love the game, it's just when my BS meter goes off i get pissed off. I love strategic games the most and as i said i was just a child then, a NORWEGIAN child then :p i'm 19 years old now and i can now see what's BS or not. So yea, the game is different from what i can remember ;p

When I was little, I hated cigarettes and smoking... so I never used the cigarettes >_>

It's a hard game. It's meant to be a hard game. It's also realistic in the way the guards are posted and what obstacles there are. During WW2, raiding heavily fortified german bases with only a handful of men wasn't all about crashing the gates and gunning down everything in sight, which is the impression you'd get from modern games.
Stealth, patience, and absolute meticulous planning is the only way to beat the game. You have to use the tools available to you in an optimal way. A very practical one is the ability to split the screen into different cameras, where you can assign a camera to that pesky patrol that keeps dedecting you, another to watch over your man who's hidden in the bushes, a third to see which way the tower guard is facing, etc. etc.