What is Defence in depth?
{{Distinguish | Defense in depth (computing)}} [[File:Sankt Georgen am Längsee Burg Hochosterwitz 01052004 2804.jpg|thumb|right|300px|{{Center|A [[medieval]] [[castle]] on a [[hill]] with multiple walls and obstacles is an [[example]] of a defense in depth}}]] {{War}} '''Defense in depth''' (also known as '''deep''' or '''elastic defense''') is a [[military strategy]]. The delaying [[tactic]] is intended not to stop the advance of an [[enemy]] but to slow it down.<ref name=Phifer102>Michiko Phifer, ''A Handbook of Military Strategy and Tactics'' (New Delhi: Vij Books India Private Limited, 2012), p. 102</ref> A defense in deep buys time by slowly yielding to the enemy and usually causes additional [[casualty (person)|casualties]]. That may slow down an advancing army and cause it to lose [[momentum]]. == Examples == [[Hannibal]] used the tactic at the [[Battle of Cannae]] in 216 [[BC]].<ref name=Phifer103>Michiko Phifer ''A Handbook of Military Strategy and Tactics'' (New Delhi: Vij Books India Private Limited, 2012), p. 103</ref> Facing a much larger [[Roman army]], he placed his less experienced [[soldiers]] in the centre<ref name=Phifer103/> and his most experienced fighters on both sides. When the Romans advanced, his centre gradually moved back, and the troops on the wings began to surround the Romans. That was the largest [[wikt:slaughter|slaughter]] of Roman soldiers in the history of the [[Roman Republic]].<ref name=Phifer103/> The classic example is [[medieval]] [[hill fort|hill forts]] and [[castle|castles]] with rings of defenses (usually [[wall|walls]]). The inner circles of defenders support the outer circles with [[missile]] fire.<ref name=Phifer103/> The attackers must breach all of the lines of defense and exhaust themselves in the process.<ref name=Phifer103/> The [[German Army]] started to use the tactic in 1917, during [[World War I]].<ref name=Daene>{{cite web |url=http://www.militaryhistoryonline.com/wwi/articles/newtactics.aspx |title=Bullets Quickly Write New Tactics |author=Roger Daene