The manoeuvres employed by the attacker can also be used by the defender to evade, or gain a tactical advantage over his opponent. Other components may also be employed to manoeuvre the aircraft, such as yaw, drag, lift, and thrust vectors. A key factor in all battles is that of "nose-tail separation". While getting close enough to fire a weapon, an attacker must keep his aircraft's nose far enough away from the tail of the defender to be able to get a good aim, and to prevent an overshoot. The defender, likewise, will use every manoeuvre available to encourage an overshoot, trying to change his own role to that of attacker.