Defilade

Defilade and enfilade 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 enfiler ("to put on a string or sling") and défiler ("to slip away or off") which the English nobility used at that time.

A unit or position is "in defilade" if it uses natural or artificial obstacles to shield or conceal. For an armored fighting vehicle (AFV), defilade is synonymous with a hull-down or turret-down position. 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. Defiladed positions on hilltops are advantageous because "dead space" – a space that cannot be engaged with direct fire – will be created in front of the position. Ideally, this dead space should be covered by the interlocking fields of fire of other nearby positions, and/or by pre-planned indirect fire such as mortars or other forms of artillery.

Artificial entrenchments can provide defilade by allowing troops to seek shelter behind a raised berm that increases the effective height of the ground, within an excavation that allows the troops to shelter below the surface of the ground or a combination of the two. The same principles apply to fighting positions for artillery and armoured fighting vehicles.