Parshas Mattos

The Rambam paskens (Ramban counts it as a mitzvah) that when conquering a city one should not to surround it from all four sides - only from three sides in order to leave room for anyone who wishes to escape. He learns it from a posuk in this week’s Parsha, (31;7) “And they formed an army against Midian as g-d had commanded Moshe”. (Based on a Sifri) They were commanded in the ways of war.
This Halacha is quite strange, why at a time when your at war with you enemy, do you let them escape, isn’t that counterproductive?
The Torah Temimah and the Meshach Chochma explain that the Rambam is giving us a brilliant strategy when going to war and in everyday life. When one is cornered into a corner he does all that he can to save himself. Ever see kids chasing a cat? The cat’s running for its life until it’s stuck and can’t get out. At that point the cat attacks and fights its way out scratching and kicking - when given no option it fights with all its might. When a city is surrounded from all four sides by the enemy and no one has any place to escape to, they will fight for their lives for they have nothing to lose - and that is a much more dangerous enemy.
(The Ramban explains that the reason for this is that it is in order for us to work on our Rachmonus- mercy and hence he counts it as a Mitzva).