Medieval commune
What did it mean for a commune member to defend another? Obviously if a commune member was attacked outside the city it was too late to call for help as it would be unlikely anyone would be around in time. Instead the commune would promise to exact revenge on the attacker, the promise of revenge being a form of defense. However, what would happen if the attacker was a noble who had a castle, too strong for the townspeople? This was often the case and certainly the town commune could not gather the people to attack a castle. Instead they might attack the nobles family, or burn his crops, or kill his serfs, or destroy his orchards. It was eye for eye violent revenge.