Basic fighter maneuvers (BFM) are tactical movements performed by fighter aircraft during air combat maneuvering (ACM, also called dogfighting), to gain a positional advantage over the opponent. BFM combines the fundamentals of aerodynamic flight and the geometry of pursuit, with the physics of managing the aircraft's energy-to-mass ratio, called its specific energy. Situational awareness is often taught as the best tactical defense, removing the possibility of an attacker getting or remaining behind the pilot; even with speed, a fighter is open to attack from the rear.