My “training rule” is a way to indicate the supplying of an unit with heavy weapons, armoured vehicles and, as i told, a global progressive mechanization of this army. All of this comprends, of course, the training of the troops to properly use this new equipments. This is, in my opinion, an historical fact, unless oil crisis…
At the strategic scale of A&A, a round is a period of at least three months (it’s a convention universally accepted, i think), and a territory, even if in the front line, is a very big extension of terrain. Entires India or UK or Germany are single territories. Islands aren’t a single rock between the ocean, but an entire “island group”: look at the New Guinea, look at the Hawaiian islands. I think that in this big territories some unit is contacting the enemy lines, but some other units are in the rearguard: this unit can be upgraded or, to call them with the name of my rule, they can be trained. If you don’t like this name, think it to “supply an unit”. ;)
And if Japan wants to reinforce its infantry in Wake Island to offer a more agreeable sacrifice to the Opening Fire of US Battleships, who am i to disapprove it? :D