hello, ı am new player of this system. while ı was playing with my friends, one of them use withdraw to pass through the behind of engagment. we let him do it for once because we couldnt remember the rules correctly. and then when ı read the rules ı couldnt see anything certain. so ım here to ask you.
It sounds like you’re asking whether a character can Withdraw into the rear of an engaging enemy. To quote the description of the Withdraw action:
Withdraw: Move away from engaging enemies at up to half combat speed. The combatant can change facing as many times as desired while withdrawing and can end facing in any direction. While withdrawing, the combatant can ignore engagement by any enemies that had him engaged at the start of the withdrawal. When his withdrawal is complete, the combatant must not remain engaged with any of the enemies that he had been engaged with. If the configuration of troops or terrain on the battlefield makes this impossible, then the combatant cannot withdraw. A withdrawing combatant can still engage, and become engaged and forced to halt by, new enemies that he encounters during his withdrawal.
This identifies first that the Withdrawing combatant only ignores engagement by characters that he began the action engaged by, and second that he cannot end the Withdrawal still engaged by them. So a character couldn’t use Withdrawal to step around someone into their flank or rear. He could use it if the defenders had a 5’ hole in their line to get behind their formation more generally, so long as he wasn’t engaging anyone who started out engaging him, but that’s hard to pull off in practice and still wouldn’t usually put him in any individual character’s rear (because of the free facing turn if unengaged).