In the next version of Merc Tactics will have a free hostage quest.
Ben Dabi soldiers will surrender if they are badly out-numbered in a battle and then will be taken hostage. Then, one of their comrades will offer a reward if you help to free them. The hostages will be kept in a locked prison building and you can either try to break them out by blowing one of the doors off, or you can just kill all the enemy and they will be freed at the end of the battle. However, once the enemy soldiers detect a break out attempt, they will try to kill the hostages, so you have to protect them.