There appears to be a bit of a contradiction in the rules regarding whether dusk brings a battle to an end.
On page 23, in Time of Day or Night, second last paragraph, it says:
If dusk occurs during a battle, fighting continues until no enemy can be seen...Once fighting ceases, both sides record their decision whether to continue the battle at dawn in their current position or retreat, then reveal it simultaneously. It ends if both sides retreat.
However, on page 43, in Victory & Defeat, first paragraph, it says:
If neither side has been defeated when a time limit is reached (or the battle has ended because one or both sides have chosen to retreat after nightfall), the game finishes at the end of the current bound.
In the first quote, both sides must retreat for the battle to end. But in the second quote, it only seems to take one army retreating to end the battle.
Is that how others read it?
While history would suggest that in most cases battles only occurred because both armies wanted to fight, and wouldn't occur if one or both sides wanted to avoid battle, may I suggest that, for DBMM, the battle should continue as long as at least one of the players wanted to continue.