public override void RemoveSoldier(Soldier soldier)
 {
     _soldiers.Remove(soldier);
 }
 public override void AddSoldier(Soldier soldier)
 {
     _soldiers.Add(soldier);
 }
 public abstract void RemoveSoldier(Soldier soldier);
 public override void RemoveSoldier(Soldier soldier)
 {
     throw new NotImplementedException();
 }
 public abstract void AddSoldier(Soldier soldier);