high closure rate by turning to increase AOT, forcing an overshoot. The AOT is often estimated by the position of the attacking aircraft's nose in relation to the defender. AOT are generally grouped into three categories, called "pursuit curves". "Lead pursuit" occurs when the nose of the attacker points ahead of the defender, while "pure pursuit" happens when the attacker's nose points directly at the defender. If the attacker's nose points behind the defender, the condition is known as "lag pursuit". Lead pursuit The primary purpose for lead pursuit is to provide closure, even when chasing a faster opponent. The high AOT presented during lead pursuit allows the attacker to quickly decrease the forward, lateral, and vertical separation between aircraft, simply by traveling a shorter path. However, lead pursuit causes the AOT to increase at a rapid rate. This causes the closure rate to increase as well, and, in an attempt to prevent an overshoot, the attacker will have to pull an increasingly tighter turn upon nearing the defender. An attacker in lead pursuit is well within the defender's rear view. Unless the defender has enough of a speed advantage to escape by relaxing the turn and dropping into a shallow dive, the defender will likely turn sharply in an effort to increase the AOT, forcing the attacker to turn even harder, to overshoot, or to perform a maneuver out of the horizontal plane to compensate. Lead pursuit is used during gun attacks, because the fast motion of combat requires that the aircraft's cannons be aimed at a point in space ahead of the defender, where the enemy will be when the bullets arrive. This is called "leading the target". Lead pursuit presents the attacker with difficulty in maintaining sight of the opponent, as the nose of the attacking aircraft becomes an obstruction to the pilot's view. Pure pursuit Like lead pursuit, pure pursuit is used to provide closure. However, closure is not as rapid, nor is the rate of increase in AOT. This is not as effective against a faster moving opponent, so the attacker may need to accelerate to maintain pure pursuit. Pure pursuit is used when acquiring a missile lock. It both places the attacker further aft of the defender and presents the defender with the smallest amount of surface area to see. This complicates evasive action, since only the front of the attacking aircraft is in