Reverse slope defence

A reverse slope defence is a military tactic where a defending force is positioned on the slope of an elevated terrain feature such as a hill, ridge, or mountain, on the side opposite from the attacking force. This tactic hinders both the attacker's ability to observe the defender's positions as well as reducing the effectiveness of the attacker's long-range weapons such as tanks and artillery.

A defending unit usually does not conduct a reverse-slope defence along its entire front, as positioning troops on the forward slope is necessary to control the region in front of the hill. However, when enemy forces are known to have superior long-range direct-fire or indirect-fire weapons, the majority of the defending force can use the hill to limit enemy observation and reduce the effectiveness of said long-range enemy fire. This tactic may even succeed in deceiving the enemy as to the true location and organisation of the main defensive positions. Typically, a smaller unit is still posted on the forward slope to perform observation and delay attackers if the defending force needs to relocate its main body onto the forward slope. Otherwise, when the attacker advances and passes over the top of the hill, they may be ambushed by short-range fire from the defender on the reverse slope and perhaps on the counterslope (the forward slope of a hill facing the reverse slope).

The best-known proponent of the tactic was the Duke of Wellington who used it repeatedly during the Napoleonic Wars to defeat the French infantry. By placing a ridge between his own army and his opponent's, and having his troops lie down, Wellington was able both to better protect his troops from French artillery fire and to strike the attacking French infantry by having his troops stand up at the last moment and deliver volleys of musketry at close range.

Examples of reverse slope defense during the American Civil war included Stonewall Jackson's defense of Henry House Hill during the First Battle of Manassas where he ordered his soldiers to lie down below the crest of the hill in order to avoid Union artillery, and Winfield Scott Hancock's counter-attack against Jubal Early at the Battle of Williamsburg. The Battle of Gettysburg was another example, especially the Union defense against Pickett's Charge, which was greatly aided by the reverse slope of Cemetery Ridge that both protected and hid infantry and large numbers of cannons that could not be easily seen by the attackers.

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