Reverse slope defence
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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; however, there are situations where subordinate units and weapon systems may be positioned on the reverse slope. This may be a wise choice when enemy forces have superior long-range direct-fire or indirect-fire weapons. The defending force uses the hill to limit enemy observation reducing the effectiveness of long-range enemy fire. It may even succeed in deceiving the enemy as to the true location and organisation of the main defensive positions. As the attacker advances and passes over the top of the hill, they may be ambushed by short-range fire from the defender.
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 protect his troops from French artillery fire and to surprise the attacking French infantry by having his troops stand up at the last moment and deliver volleys of musketry at close range. The French were beaten so often in this manner that Wellington was prompted to comment, "They came on in the same old way and we defeated them in the same old way."
American Civil War
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 which both protected and hid infantry and large numbers of cannons that could not be easily seen by the attackers.
World War II
After the capture of Carentan by American paratroopers, German forces (elements of the 17th SS Panzergrenadier Division and 6th Fallschirmjäger Regiment) counterattacked in an attempt to recapture this strategically vital town on 13 June 1944. Elements of the U.S. 101st Airborne Division (502nd and 506th Parachute Infantry Regiments (PIR)) met the enemy advance southwest of Carentan at the Battle of Bloody Gulch.
The terrain offered the Americans the opportunity of a reverse slope defence and two companies of the 506th PIR lined up along the hedgerows at the bottom of Hill 30. The American troops were outnumbered and being hit with tank and assault gun fire, but the reverse incline enabled them to direct all their firepower at the Germans as they appeared over the top of the hill. Although they were almost overrun, their position gave them enough of an advantage to hold their ground until they were relieved by the U.S. 2nd Armored Division.
Reverse slope defenses were very popular with the Japanese during the island campaigns in the Pacific theater. American superiority in naval support artillery prompted the Japanese to shelter on reverse slopes until they could engage American troops at close range.
During the Falklands War, the Argentine defensive positions were positioned on the forward slopes. During the Battle of Wireless Ridge, the British 2nd Battalion, The Parachute Regiment (2 Para) occupied Argentine positions on a reverse slope, protected from Argentine artillery fire.
At the Battle of 73 Easting , M1A1 tanks of Eagle Troop led by Captain McMaster crested a hill and surprised an Iraqi tank company set up in a reverse slope defence on the 70 Easting. They immediately engaged the Iraqi tanks and destroyed the company.
- Lord Montagu of Beaulieu speaking in the House of Lords Hansard: 24 Apr 1996 : Column 1172, paragraph 4
- Infantry Tactics and Combat during the Napoleonic Wars ~ Part 3 ~ Columns. This article argues that all armies of the period used column formations at times on the battlefield, the military historian Sir Charles Oman is credited with developing the theory that the French practically always attacked in heavy columns, and it is only now that this alleged error, propagated by other British and American authors, is being repudiated. (see also Historical revisionism: French attack formations in the Napoleonic wars)