Enfilade and defilade

A unit or position is "in defilade" if it uses natural or artificial obstacles to shield or conceal itself from enfilade and hostile fire.

[4] Although sophisticated archery tactics grew rare in Western Europe during the Early Middle Ages, enfilade fire was reemphasized by the late medieval English using ranked archers combined with dismounted knights, first employed at the Battle of Dupplin Moor in 1332 and used to devastating effect against the French in the Hundred Years War.

Enfilade fire takes advantage of the fact that it is usually easier to aim laterally (traversing the weapon) than to correctly estimate the range to avoid shooting too long or short.

When planning field and other fortifications, it became common for mutually supporting positions to be arranged so that it became impossible to attack any one position without exposing oneself to enfilading fire from the others, this being found for example in the mutually supporting bastions of star forts, and the caponiers of later fortifications.

Defilade is also used to refer to a position on the reverse slope of a hill or within a depression in level or rolling terrain.

Early detection and elimination of antitank threats is an important reason that tanks attack with infantry support.