Jason Liang
Arcane
As unintuitive as it seems, the best strategy isn't to balance your efforts.I mean i tried my best to balance out my operation phases by prioritizing the country with the most difference in casualty and prep phase with the 2nd mostBattle advantage increases when you do a primary mission in that region (ie, kill a majin or a general). Then it decreases every turn afterwards.
When you score a major victory after suppressing both fiends in a country, it's actually best to press your advantage there by following up with the skirmish mission there next turn, so that the country will self liberate earlier. When a country is liberated, it's troops will be assigned to fight in the other countries. This is important when trying to achieve the Grand Invasion (land) ending.