Apparently the requirement is only single digit but the reality is that a double-digit army is necessary. I can't think of a single decent map that doesn't support double-digit armies in every territory.
|>All territories must be big enough to completely fit their army number. Often people's first instinct is to keep territories real-life sized, however this doesn't work well in WarLight's engine. Take, for example, Hawaii in the main Earth map. Hawaii is a very small island, but in the Earth map it's sized significantly larger so that it can fit the army number. In the map designer, you'll find a button labeled Show Example Armies. When clicking this, all territories must be big enough to fit the entire army number.