The South Setup:
I tried to get at least 5 factors per attackable hexside arranged here. I came close. Both cities have the abilitiy to defend with 18 factors (including the ART in the south). Of course, Kiev only gets 16 factors of defense if the Germans don't use any armor for the attack. Either way, it's likely to be costly for Germany to take anything here. But I haven't actually run those calculations. I'll do that when I'm into the German impulse.
-----
As Germany, I think I may need to move up to the lines, see if I can successfully attack anything (probably not), and then take an Air Action next impulse. It may seem like a waste of an impulse, letting the Soviets retreat if they so desire, but right now I have 10 organized aircraft too far behind the lines to be of any use. Additionally, since it will be getting toward mid-turn (maybe), I could even use HQ-I von Bock to reorganize 3 of the LND that I've already used up.
-----
As the Soviets, I don't know how I would respond to this. I should play the next Soviet impulse as if I don't expect an Air Action by the Germans, I think. That means holding the line, doesn't it? Because if I do begin what I "expect" to be 2 impulses of retreat to the Don, the German player (me) can always change his mind and take another Land Action.
So, after trying to hold the river line next impulse, if Germany takes an Air Action after that, what do I do? Hold the line? or try to retreat?

Always listen to experts. They'll tell you what can't be done and why. Then do it!
-Lazarus Long, RAH