If the point of the wedge can breach the enemy line, the following troops can widen the gap. As successive ranks of the wedge engage, they can draw their opponents' attention away from previous ranks, thereby protecting them.
The tactic has been especially effective when used by armored and heavily-armed infantry against shield wall defensive formations, where defenders link their shields to form an all-but impenetrable wall. The wedge can be used to knock a small section of the wall open, and flank the enemy from inside their own line. This can be the reason of its use by the Viking and Germanic peoples of the Medieval years, since they also deployed in shieldwall.
This tactic relies on momentum and penetration. If the point of the wedge can be stopped for even a moment, the wedge can be easily enveloped in a pincer attack. The wedge is still used in modern armies, especially by tanks and other armored units. An example of this is the Panzerkeil or "armored wedge" used by the Germans in World War II.
The wedge formation is used ceremonially by cadets at the United States Air Force Academy during the annual graduation parade, when the soon-to-be commissioned first-class cadets (seniors) leave the Cadet Wing. This is the reverse of the acceptance parade, held each fall, when the new fourth-class cadets (freshmen) join the Cadet Wing in the inverted wedge formation.
The wedge in Antiquity and medieval warfare
The wedge (έμβολον, embolon in Greek; cuneus in Latin, colloquially also caput porcinum, "boar's head"), was used by both infantry and cavalry. The men deployed in a triangular or trapezoid formation with the tip leading the way. According to Arrian and Asclepiodotus, the wedge was first used by the Scythians, and then the Thracians. Philip II of Macedon adopted it from them as the main formation of his Companion cavalry and Alexander the Great faced Persian cavalry arrayed thus, as Arrian attests. The use of this formation enabled the concentration of missiles against a limited front and thus was used not only to smash into the enemy line, but to also add to the effectiveness of long range, usually hurled weapons like javelins and hand axes. As an infantry formation it is attested by Frontinus to have been used by the Romans in Pydna against the Macedonian line of Perseus. It was also used to great effect by the Roman legions, with the wedge proving effective in campaigns in Britain, such as during Boudicca's Revolt, where a greatly outnumbered Roman army used it to defeat the Iceni. In the Late Roman army, several cavalry units were designated as cuneus [equitum].
A complete description of an infantry wedge is given by Saxo Grammaticus in his Gesta Danorum. He depicts it as a formation 10 men deep with the first rank being composed of 2 men, each rank composed of 2 more. Thus, each Viking wedge was composed of 110 men, 10 deep, 2 men on its tip, and 20 on its base. According to the Vikings, the wedge formation, called by them svinfylking, cf. the Latin caput porcinum, was invented by Odin himself .
Byzantine Emperor Nikephoros Phocas analyzes the wedge formation of the Byzantine Cataphracts in the third chapter of his Praecepta Militaria. There, he relates that the wedge must be formed by 354 cataphracts and 150 horse archers to a total number of 504 men. The row of the first line comprised 20 horsemen, the second 24, the third 28, down to the 12th line, which consisted of 64 men. If such a number of men is not available, he proposes that the wedge be formed by 304 cataphracts and 80 horse archers, or a total of 384 men, the first line comprising 10 men. In his next chapter (Ordinance on Cavalry Deployment), he ordains that the wedge must be accompanied by two cavalry units, which will guard its flanks.
A wedge whose ranks are not complete in the middle is shaped as an Λ instead of a Δ and is called a hollow wedge, or in Greek κοιλέμβολον, koilembolon.
Police riot squads sometimes charge in flying wedge formations, to break into a dense crowd as a snatch squad to arrest a leader or speaker, or to chop a long demonstration march into segments. It can also be used to escort VIP's through hostile crowds.
The formation can also apply to sports, particularly a formation in American football that was introduced by Harvard in an 1892 game against Yale. Identical in concept to the military formation, the flying wedge was known for being brutally effective, but also resulting in a high rate of injury on both sides. Because of a number of injuries suffered in college football, this and similar formations were banned in 1894, though its concept remained in certain modern football plays. In 2009, NFL league owners strengthened the ban to completely disallow any type of blocking wedge formation The flying wedge is also (for similar safety reasons) banned in Rugby Union.