Several units bid in same area are allowed ?
In a ‘Tournament of Champions’ file I’ve seen 3 inf in UKR are enough to deter Russian attack and give Germany a lasting edge.
In the Ladder (1 unit per area!) my recent favorite is 1 tank in Libya (or Algeria) and Japanese 1 arty in Indochina. Helps greatly with the usual J1 fighter crisis, to the point that Allied don’t dare so many threats at once, so the arty is a bit superfluous (I’ve attacked China with 5inf,1arty, 3 ftr) and taken empty India.
A nice paradox - Without the arty, it’s badly needed. With the unit it’s not needed any more…