Shield wall

The wall, (Scildweall or Bordweall in Old English, Skjaldborg in Old Norse) is a military tactic that was common in many cultures in the Pre-Early Modern warfare age. There were many slight variations of this tactic among these cultures, but in general, a shield wall was a "wall of shields" formed by soldiers standing in formation shoulder to shoulder, holding their shields so that they abut or overlap. Each man benefits from the protection of his neighbour's shield, usually the man to his right, as well as his own.

Ancient times
This tactic was used by many ancient armies including the Persian Sparabara, Greek hoplite phalanx formation, and Roman legions.

The shield wall came into use in ancient Greece during the late eighth or early seventh century BC. The soldiers in these shield wall formations were called hoplites, so named for their heavy weaponry (hopla, "ὅπλα"). These were three-foot shields made from wood and covered in metal. Instead of fighting individual battles in large skirmishes, hoplites fought as cohesive units in this tight formation with their shields pushing forward against the man in front (to use weight of numbers).The left half of the shield was designed to cover the unprotected right side of the hoplite next to them. The worst, or newest, fighters would be placed in the middle front of the formation to provide both physical and psychological security.

Roman legions used a type of shield wall called a testudo formation in which the first row formed a dense vertical shield wall and the back rows held shields over their heads, thus forming a tortoise-like defense, impenetrable to missile weapons. The man at the right hand of each warrior had an important role; he covered the right side of the warrior next to him with his shield. This made it so that all the shields overlap each other and thus formed a solid battle line. The second row was to kill the soldiers of the first line of an enemy shield wall, and so trying to break it. All the other rows were weight for the pushing match that always occurs when both sides tried to break the other wall. When a wall was broken the battle turned into a single-combat melee in which the side whose wall collapsed had a serious disadvantage.

In the late Roman army and the Byzantine army, similar formations of locked shields and projecting spears were called fulcum (φοῦλκον, phoulkon in Greek), and were first described in the late 6th-century Strategikon. Roman legions were typically well-trained, and often used short stabbing-swords (such as the Gladius) in the close-quarters combat that inevitably resulted when their shield-walls contacted the enemy. Auxiliaries were often less armed, therefore to provide more defence a shield-wall with spearmen was commonly used.

Early Medieval Period
The shield-wall was commonly used in many parts of Northern Europe, such as England and Scandinavia. In the battles between the Anglo-Saxons and the Danes, most of the Saxon army would have been the fierce but inexperienced Fyrd—a militia composed of middle class freemen. However, the shield-wall tactics of the day did not require extraordinary skill, being essentially a shoving and fencing match with weapons. A few select warriors, such as Huscarls and Thegns, carried heavier weapons and consistently wore armour. There would also have been nobles such as Thegns and Earls who would have had their own armoured retainers. These men made up the first three ranks of the main wall, and as bodyguards for highly placed Thegns and royalty.

The vast majority of opponents in such battles were armed with spears, which they used against the unprotected legs or faces of their opponents. Often, soldiers would use their weapons to support each other by stabbing and slashing to the left or the right, rather than just ahead. Short weapons, such as the ubiquitous seax, could also be used in the tight quarters of the wall. Limited use of archery and thrown missile weapons occurred in opening stages of shield-wall battles, but were rarely decisive to the outcome. The drawback of the shield-wall tactic was that once breached, the whole affair tended to fall apart rather quickly. Relatively lightly trained fyrdmen gained morale from being shoulder-to-shoulder with their comrades, but often fled once this was compromised. Once the wall was breached, it could prove difficult or impossible to re-establish a defensive line, and panic might well set in among the defenders.

The tactic was used at the Battle of Stamford Bridge, where the relatively well-armed Saxon army hit a Viking army unaware. The Vikings were not wearing as much armour, having left their mail behind on the ships and wearing only their helmets, and after a bloody shield-wall-versus-shield-wall battle, fled in panic. Both sides lost 5-6000 each but the numerical superiority of the English won the battle. Both sides at the Battle of Hastings are clearly visible in the Bayeux Tapestry using the tactic, though a combination of Norman mounted cavalry and the impetuousness of less experienced Saxon warriors ultimately won the day—portending the end of massed shields in combat. However, it must be said that, even with the use of shieldwalls, battles rarely lasted more than an hour. The battle of Hastings, on the other hand, lasted for 7 hours, and very nearly went the other way—William was unhorsed twice, and the battle may have ended just fifteen minutes before the fall of darkness. Massed shieldwalls would be employed right up to the end of the 12th century, especially in areas which were unsuitable for large scale mounted warfare, such as Scandinavia and Scotland.

Decline
The shield-wall as a tactic has declined and has been resurrected a number of times. For example, in the Greek and Macedonian phalanxes, as the Dory spear gave way to the sarissa, it became impossible to carry a large shield and so it was abandoned.

Likewise, in the Late Middle Ages, the shield was abandoned in favour of polearms carried with both hands, giving rise to the pike square tactics.

In the revival of military thinking and tactics that was a part of the Renaissance, military theorists such as Niccolò Machiavelli in his The Art of War advocated a revival of the Roman legion and Sword and shieldmen. But as in the phalanxes before, well-drilled pikemen displaced the shieldmen.

The pike square remained in use on the European battlefields of the 16th and 17th centuries, but with the increasing importance of the handgun, it was replaced by the line and column formations in the 18th century.

Use in modern times
Although largely obsolete as a military tactic due to firearms, a wall of riot shields remains a common formation for riot police worldwide. Modern riot shields can not be designed to adequately provide ballistic protection against firearms while remaining light in weight, but can still protect the police officers against objects (such as bricks or bottles or even Molotov cocktails) that are thrown towards the riot police.