Yes as of now this only applies to land battles, because in most A&A games there is no strong mechanism for control of sea zones. Basically because of how subs and transports now work, it is possible for the enemy to still be inside a sz under your control after the combat phase concludes, and there aren’t enough control markers in the box to place them in all sea zones. But this rule could potentially be adapted to encourage the naval game, if you had enough chips and the desire to figure out how you wanted to handle “control” of sz.
For now though, with the land battles, the rule has the following gameplay effects:
It encourages attack fanning, the attacking of multiple territories during a turn, as opposed to the stack push you have more reason to send the units forward even if likely to take more losses because the +1 bonus is a driver.
Encourages the attack and capture of low or no value territories, since the bonus applies equally to all land territories on the game map.
It provides a slight disincentive for what might be called the narrow “stafe” where at the last minute the attacker decides to just “go for it” because the +1 ipc is a draw.
Slightly encourages or at least provides an incentive for the continuous push or spread of infantry, rather than the defensive grind and fortification, which leads to somewhat faster game resolution.
In terms of overall balance, because the Axis generally start in expansion mode, they generally receive the stronger battle bonus early, whereas Allies tend to get more out of it in the later rounds (once they’ve positioned themselves for Amphibious and reconquest). This fits reasonably well with the general model that has Axis pushing early, to try and hit the crescendo, before the pendulum swings the other direction and Allies start mounting more attacks each round.
