Enfilade and defilade

Enfilade and defilade are concepts in military tactics used to describe a military formation's exposure to enemy fire. A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. A unit or position is "in defilade" if it uses natural or artificial obstacles to shield or conceal itself from enfilade. The strategies invented by the English use the French ("to put on a string or sling") and ("to slip away or off") which the English nobility used at that time.

Enfilade fire, a gunfire directed against an enfiladed formation or position, is also commonly known as "flanking fire".Raking fire is the equivalent term in naval warfare. Strafing, firing on targets from a flying platform, is often done with enfilade fire.

A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. For instance, a trench is enfiladed if the opponent can fire down the length of the trench. A column of marching troops is enfiladed if fired on from the front or rear such that the projectiles travel the length of the column. A rank or line of advancing troops is enfiladed if fired on from the side (from the flank).

The original concept of enfilade fire was invented by the 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. The benefit of enfilading an enemy formation is that, by firing along the long axis, it becomes easier to hit targets within that formation. 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. Additionally, both indirect and direct fire projectiles that might miss an intended target are more likely to hit another valuable target within the formation if firing along the long axis.

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

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