Enfilade and defilade

Enfilade and defilade are military tactical concepts describing a formation's exposure to enemy fire. A position is "in enfilade" if weapon fire can be directed along its longest axis, such as a trench fired upon along its length or troops advancing in a line struck from the side. Enfilade fire, also known as flanking fire, allows attackers to target multiple enemies with lateral shots, which are easier to aim and more likely to hit additional targets within the formation. This tactic has been used since antiquity, notably by medieval English forces during the Hundred Years' War, who combined archers and dismounted knights to devastating effect.

Defilade refers to a position shielded by natural or artificial obstacles, such as hills or entrenchments, protecting troops from direct fire. Defiladed positions on reverse slopes create "dead space" that cannot be engaged with direct fire, forcing attackers into vulnerable enfiladed positions when advancing. This tactic is particularly effective for antitank weapons, as it neutralizes the tank's range advantage and exposes thinner armor when the tank crests a hill. Artificial defenses like berms or excavations also provide defilade by lowering troop exposure.

A combination of these tactics allows defenders to remain protected while enfilading advancing enemies. Enfilade fire is also used in naval warfare (raking fire) and aerial attacks (strafing). Both concepts have been integral to fortification design, such as star forts and bastions, ensuring mutual support and exposing attackers to flanking fire.