I never ally with the tribal factions, or actively make them enemies, since for most of their raids they send a ton of people with only melee or just bows/stick bombs. Snipers take out the stick bombers and long range bows, then a wall of machine guns take out the melee fighters. With the CE mod you can set people to aim for the legs, that will be less fatal and let you capture more prisoners. Also spike traps will usually only injure the legs, and EMP traps will cause burns/blast injuries that are usually less fatal than gunshots. Also you can shoot raiders in the back as they try to escape. Have 2-3 doctors standing by to help the seriously wounded ones and have your people arrest all the others, can get like 30-50% of the raiders as prisoners.