I 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!  Whew!