Now, if Germany lands lots of ftrs in fin on Rd 1 (to hold Fin for rd 2), you must attack to take those ftrs out, IMO.
Now based on your other posts about your games, I’m assuming Ger is attacking Kar on rd 1.
But assuming you hold Kar, and have a few inf in Kar left over with 3 arm and 2 ftrs, you can attack Fin with everything you got in Kar (to kill the ftrs), then place only 1 inf in Kar, and the rest in Moscow. Now you’ve set a little trap for the Germans. If they attack Kar you can hit them with your combined forces from Mos and Fin and easily reclaim it. However, if things go bad, you can “leap frog retreat” and retreat everything back to Moscow after you do a round or two of strafing to weaken the Germans.
Again though, I think you’ll stop seeing Germany load up in Fin if you stack 19 inf, 3 arm, 2 ftrs in Kar at the end of Russia 1. Again, there is no way Germany can hit this on G1 without bringing in all their airforce (or a bid), getting extremely lucky and even then they only hold with an arm while losing all their air. Which means UK can counter with 2 inf, 1 arm, planes and BB shot, then Russia can still place 8 inf on Kar in rd 2.