public void ChangeState(TroopState state)
    {
        if (troopState != null)
        {
            previousTroopState = troopState;
            troopState.Exit();
        }

        troopState = state;
        troopState.Enter();
    }
 public void ChangeToPreviousState()
 {
     troopState = previousTroopState;
     troopState.Enter();
 }