Completed this level first of all by literally taking out everyone a man at a time, and boy was it hard going! Then my brother tried it, and discovered that when you've sniped one nazi from the Russian embassy (be careful, pop out of the wrong window and the elite sniper will kill you!), and cleared out the Nazi riflemen around the fountain by sniping them from the unoccupied yard area (behind the wall, above the little dugouts the Russians soldiers mostly start in), you can crawl down, take their stuff and then as you move down towards the highest tower (it's a church building), the elite nazi sniper should move his position and make a run for it; he tends to respond to your movements to keep you covered so you can't snipe him but he can snipe you. As he runs, you can actually quite safely change direction, bolt the other way and snipe him as he's running - ending this part of the mission early!