窮寇莫追 is an idiom originated from a military motto. It means "do not pursue a desperate foe"
There are few possible explanations for this military motto
1. If you caught up with an defeated army, out of desperation, they may fight you to the death and cause great damage to your own ranks.
2. It could be a trick that designed to lure you into an ambush.
3. To pursue a fleeing army means your army has to break its own formation. if they are attacked at this moment, they can't defend themselves.
4. To destroy an entire fleeing army may be considered wanton slaughter (you don't do it unless you really want to destroy an entire army, willing to take the risk of being ambushed and take the blame for a massacre)
There are few possible explanations for this military motto
1. If you caught up with an defeated army, out of desperation, they may fight you to the death and cause great damage to your own ranks.
2. It could be a trick that designed to lure you into an ambush.
3. To pursue a fleeing army means your army has to break its own formation. if they are attacked at this moment, they can't defend themselves.
4. To destroy an entire fleeing army may be considered wanton slaughter (you don't do it unless you really want to destroy an entire army, willing to take the risk of being ambushed and take the blame for a massacre)