Defilade & Enfilade

Defilade (pronounced def-uh-leyd or def-fuh-lahd)

(1) In military tactical planning and battlefield practice, the protection from hostile ground observation and flat projecting fire provided by an artificial or natural obstacle such as a hill.

(2) The disposition of defensive fortifications to produce this protection.

(3) A fortification having such protection.

1828: From the French défil (to unthread), the construct being dé (remove) + filer (thread), from the Latin fīlum (thread).  The -ade suffix was a borrowing of the Spanish -ado, from the Latin -ata (feminine -atum) used to create adjectives, nouns, and sometimes verbs from words ending in -a.  The suffix was used to form nouns denoting action, or a person performing said action.  The Old French verb was borrowed by Middle English as défiler (to slip away or off), use apparently restricted to the nobility.  The related forms are defiladed & defilading.

Enfilade (pronounced en-fuh-leyd or en-fuh-lahd)

(1) In military tactical planning and battlefield practice, a position of works, troops and matériel which permits sweeping fire from along the length of a line of troops, a trench, a battery etc.

(2) The fire thus directed.

(3) In architecture, an axial arrangement of doorways connecting a suite of rooms with a vista extending the entire length of the suite.

(4) In interior decorating, an axial arrangement of mirrors on opposite sides of a room so as to give an effect of an infinitely long vista.

1697: From the French enfil (to thread), the construct being, en (put on) + filer (thread), from the Latin fīlum (thread).  The -ade suffix was a borrowing of the Spanish -ado, from the Latin -ata (feminine -atum) used to create adjectives, nouns, and sometimes verbs from words ending in -a.  The suffix was used to form nouns denoting action, or a person performing said action.  The Old French verb was borrowed by Middle English as enfile (to put (something) on a thread or string), use apparently restricted to the nobility.

The use in architecture (mostly to describe rows of apartments) and forestry (referencing rows of trees) predated the military sense which now predominates, the original definition in that context printed in military manuals as “rake with shot through the full length”.  The use in architecture persists though it’s long tended to be used loosely to refer to just about anything in a straight line.  Used as a verb since 1706, the related forms are enfiladed & enfilading. 

Known also by the more helpful expression “terrain shielding”, enfilade and defilade are concepts in military tactical theory used to describe a formation's exposure to enemy fire.  A static position is said to be "in enfilade" if an opponent can direct continuous fire along its longest axis.  A static position is "in defilade" if formed with natural or artificial obstacles to shield or conceal the formation from enfilade.  The military picked up the terms from two Old English borrowings from the French: enfiler to put (something) on a thread or string) and défiler (to slip away or off) used (seemingly exclusively) by the English nobility.  In gunnery, enfilade fire (gunfire directed against an enfiladed formation or position) is known also as "flanking fire"; the preferred Admiralty terms for naval fire being raking fire (although the advent of long-range missiles as the warship’s standard armament (big guns now quite rare) means the concept is at sea, now essentially historic.  Strafing, the firing on ground targets from a flying platform, should be done with enfilade fire, the recommendation being (if possible) to maneuver into an enfiladed position prior to attack.  In just about any situation, the enfiladed position is the most advantageous, and thus most sought, for the attacking force.

NATO defines the parameters of the defilade as (1) protection from hostile observation and fire provided by an obstacle such as a hill, ridge, or bank, (2) a vertical distance by which a position is concealed from enemy observation and (3), to shield from enemy fire or observation by using natural or artificial obstacles.  However, the standard definition reflects the origin of the concept in the pre-mechanical age.  In anti-tank (or other armored vehicle) operations, it can be advantageous to generate enfilade fire with anti-armor weapons, from a defilade position, armor tending to be weaker on the sides and rear of armored vehicles so side shots (enfilade) offer greater penetrative potential.

The practical employment of the defilade position need not require construction and may be achieved by taking advantage of a favorable feature of the natural environment such as a ditch, the tactical significance being the enemy is engaged not from the front but from the flank using enfilade fire, the font being protected with hard cover. Used thus, ground to the front will be covered by mutually supporting positions firing from defilade, both sides firing across the front.