M-200% No. 6

What you wrote about retreating is exactly as stated in the rules: fighting is only possible if the shackles are worn.

Miscellaneous
If a stalemate situation occurs in battle, the attacking player must retreat. For example: the attacker has 100 gnomes remaining during the battle, while the defending hero has 1 fly. And the 100 gnomes cannot catch the fly. In this case, the attacker with 100 gnomes must retreat (or pay a ransom). If someone is wearing "war shackles," you need to load the last save, repeat all moves exactly as they were made before this battle, disband the troops that were killed during this battle. Then, the player(s) wearing the shackles must remove them, the attacker must attack, and then retreat/pay a ransom.
I think you've confused something in the rules.