Straddling the line between body armor and weapon is the shield. A shield is a hand held barrier used to deflect or otherwise stop incoming blows. Usually a shield would be carried in the user's secondary hand while the favored hand would carry a weapon (the right hand in most cases). Shields have been in use since at least the neolithic period, and have been used by people from Europe to Australia to the Americas. Shields have been constructed from a variety of materials, including woven reeds, animal hides, and textiles over frames made of wood, bone, or metal.
Shields in Warfare
While swords and axes gets all the glory in fantasy literature, the humble shield is probably the most ubiquitous piece of equipement that could be found on the battlefield. If you look at any ancient depiction of a battle you will see plenty of different weapons around, but nearly everybody that was not using 2-handed weapons would carry a shield, from the knight in shining armour to the lowly peasant.
The first well-attested military formation to make good use of the shield was the Greek Phalanx, a square formation of heavy infantry. The soldiers, standing shoulder to shoulder, locked their shields toghether forming a wall, then pointed their spears forward and starded marching. With a judicious use of the Phalanx Alexander The Great steamrolled half of Asia, creating one of the greatest empires of the ancient world.
Similar to this formation - albeit armed with swords and javelins, not with 8-9 foot long pikes - was the famous and equally effective Roman testudo. The tetsudo, along with a couple of innovations like 'squads' and more flexible battle-lines, were used to steamroll Europe and create another big-ass Empire. If you're starting to see a pattern here, congratulations: you've just passed Ancient History 101. Every culture in ancient to medieval warfare used a form or another of the shield wall for their infantry, the alternative being quickly and mercilessly butchered and forgotten. They stopped only with the introduction of artillery, that made tight formations nothing but a huge target and hence highly inadvisable.
Outside of strictly military use police forces everywhere still uses riot shields when they need to quell any particularly virulent revolt or need to get up close and personal with some protesters.
In addition to defense, shields can also be used offensively. A good solid shield is a broad heavy object, and it can be used to bash people. A blow to the head would cause great damage even to an armoured enemy, and could kill or at least disorient the opposition. The Romans were very fond of this. Some forms of shield had spikes added to them in order to make the most out of bashing attacks.
Another way to use a shield is not to use a shield, carry only a weapon leaving the shield work and defense to another guy you had trained with, namely the Shield Bearer. The shield bearer is often talked about in ancient texts and while he may have just been slave who carried the heaviest chunk of gear, he could also have been a highly trained solider who fought with and defended the swordsmen. Evidence for trained shield bearers comes from various Middle Eastern Bronze Age sources, such the Old testament where Jonathan and his shield bearer routed a philistine advance guard unit of maybe 20 guys, and from the Egyptian New Kingdom, in which chariots were often described as being crewed by a warrior/driver and shield-bearer. The (extremely biased and propagandist) poem describing the Battle of Qadesh on the walls at Karnak has Ramesses II giving a speech to inspire his wavering shield bearer.
Types of Shields
- Buckler: The smallest of the shields, no bigger than 6-18 inches in diameter and light enough to be held in one fist, often made of metal with a leather fronting. They were also one of the few shields light enough to be regularly carried on one's person (let's be honest, how many knights do you think carried a full-sized shield on their back at all times?), as it was meant for personal defense rather than warfare, although it was often carried as a backup defensive weapon by infantry during the 14th and 15th centuries, such as Archers or Billmen, and is sometimes listed as issued (livery) kit for levies in English muster rolls. It was too small to block arrows and projectiles, but its light weight made it excellent for protecting the sword hand and deflecting an enemy's weapons in melee combat. It could also double as a punching weapon. The term "swashbuckler" comes from the rather theatrical fighting style employed by the swordsmen who favored fighting with a sword and buckler. The English and the Spanish were both famous for their sword and buckler fencing.
- Heater Shield: Named by Victorian antiquarians for their similar shape to a clothes iron, heater shields were relatively light while still providing a fair degree of protection, making them an ideal form of protection when paired with a sword. (This is the shield most people think of when they think of a sword-and-shield combination.) Heater shields became dominant both for their ease of use, and the fact that more advanced armors meant that shields didn't need to cover the whole body, they just needed to deflect blows. This was emphasized by the way they blocked; whereas older and larger shields block in a punching motion, heaters are used to push enemy weapons away from the body. Later versions had small notches just large enough for the user to place his lance on it as a guide while jousting. They were often carved from a single piece of wood, and could have laminations of bone or horn, with canvas or rawhide outer layers, and thick pads of wool or fabric on the back to protect the shield arm. Heater shields made entirely from metal are a completely modern invention.
- Hoplon: A large round shield made of wood with outer layers of bronze. It was one of the most important pieces of equipment for classical Greek heavy infantry called Hoplites. It was employed to devastating effect in the famous Phalanx formation, the most powerful military tactic for several hundred years, capable of crushing enemy armies many times their size through superb defense and nigh-unbreakable lines. The main advantage of the Hoplon was that the shields easily overlapped with one another to form an extremely sturdy shield wall. The Hoplon was eventually replaced with a much smaller shield only because the Greeks realized that they didn't even need shields if they could just use really long spears and overlap them five layers deep, preventing any enemy from even getting close. It should be noted that, while many round wooden shields existed, the term Hoplon is used almost exclusively to describe the Greek variety.
- Some other, less well-known Greek shields include the thyreos/thureos oval-shaped shield which became common around 3rd BC (reflecting developments in making infantry more versatile than the slowly-moving spiked walls that were Hoplites), and peltasts (essentially skirmishers) were, like, hoplites, originally named for their using a unique crescent-shaped shield called a pelte. The aforementioned smaller shields used by later phalanxes above was believed to have been called a Telemon or pelta shield.
- Round shield: A common early historical shield made of wood, with a large and prominent metal boss in the center. This was the favored shield of Vikings and other early medieval forces. While the soldiers wielding them didn't perform Testudos or Phalanxes like their ancient counterparts could, the shield was large and serviceable enough for even hastily trained militia to form a basic shield wall by interlocking shields.
- Scutum: A massive shield almost as large as a man's body that was the mainstay of the Roman legions, and possibly the most widely-produced shield of all time. These were often used alongside a javelin and gladius to either charge at an opponent or to provide cover when throwing javelins. A particularly favored formation that utilized the scutum was the testudo (literally "tortoise")- the soldiers on the front and sides of the formation would hold their shields outward, while the remainder would overlap their shields above the heads of the formation, creating a box over themselves which was invaluable in siege warfare for its ability to block attacks from all sides (mainly projectile attacks; because of how tight and difficult it is to see and move in this formation, it was not recommended for melee. One of the worst defeats even dealt to the Romans at the Battle of Carrhae happened because Parthian horse archers with a baggage train of ALL OF THE ARROWS forced the Romans in advance in testudo, allowing the Parthian heavy lancers to charge them to death as piecemeal). This is what most often comes to mind when you mention "tower shields" in RPGs.
- While the classic large rectangle is the Roman shield in popular consciousness, Rome's military eventually switched to smaller, oval shields called a Skutos. Smaller, round shields also saw use in Roman hands; from skirmishers to eventually frontline infantry, foreshadowing the shields that would be used for some centuries in the wake of the fall of the Western Roman Empire.
- Pavise: Imagine something between smaller doors and Scutum. This shield was really big, able to cover a user's entire body up to the chin. It originated in Italy, but quickly became popular in late 14th and early 15th century all over Europe. It was usually used to cover crossbowman, who could reload his weapon behind the shield (yeah, some pavises got a "stick" on the backside, so they can stand without someone actually holding them). On the other hand, Czech Hussites took those shields, mixed them with battlewagons (actually used as mobile trench/firepoint), early gunpowder weapons and all sorts of choppy-and-pointy things on a sticks and managed to run a 15 years of religious rebellion (and yes, it's not lost on us that they basically invented the tank). They were popular with many lower ranking infantrymen during the 15th century since they mitigated the effect of wearing cheaper armour by defending more of the body. As a result, commoner infantry were often called "pavisiers".
- Targe: A relative of the buckler developed in Scotland, targes are round shields about 18-21 inches in diameter with two loops on the back- one for the arm to pass through and another to be held in one's hands, essentially allowing the wielder to have some degree of protection even while wielding a two-handed weapon (e.g. a claymore) or allowing one to use a pistol or dirk in the shield hand. The center of the shield was frequently equipped with a large spike, making it fairly effective as a weapon on its own as well. (Fun fact- the term "target" is derived from the general size and shape of the targe.) This shield in particular saw use much later in history alongside guns for the Scottish "Highland charge", where the Scots took advantage of muskets' poor fire-rate by approaching close, shooting, crouching down low to avoid the return volley, dropping unnecessary equipment, then charging the enemy line; using their targe to deflect the swords or bayonets their English adversaries tried to defend themselves with before landing a killing blow against them while they were vulnerable with a one-handed blade. This tactic was eventually defeated by the English regulars being trained to alleviate the targe pushing off their bayonets away and not (understandably) completely-lose-their-shit by stabbing at the other Scot to their left regardless.
- Kite Shield: A large shield with a distinctive upside-down teardrop shape which allowed users to guard both the forelegs and the upper body. As body armor became more prevalent (thus minimizing the need for leg cover), it was eventually superseded by the heater shield. This type of shield worked well for Norman cavalry, as the extra length afforded protection for both the rider and the horse. As with the heater, they were never made from metal.
- Riot and Ballistic shields: Shields are still being made, albeit relegated to situational uses (mostly within riot control divisions of law enforcement agencies). Ballistic shields are used when storming a house by SWAT troops expecting to fight in close quarters and are made to stop rifle rounds or shotgun shells. Riot shields are on the other hand made more to stop people using improvised weapons like rocks and Molotov cocktails (but are still reasonably effective against small caliber gunfire) and are also used to form shield "Walls" to physically stop an unruly mob (on a bad enough occasion, they might be even seen forming a testudo!). Both kinds are either made of transparent plastics or have a small slit in the middle to allow the user to see while still keeping the shield up, allowing a sidearm or PDW to be fired with an acceptable degree of accuracy while advancing.
- Gun Shield: A metal shield with a breech-loading pistol barrel in the center, the Gun Shield was created by commission for King Henry the VIII, practically on a whim. Despite being too heavy to effectively aim, and impractical to attempt to reload, the king was enamored by the idea of this weapon for his bodyguard and ordered a hundred, where they promptly proceeded to gather dust.
- Lantern Shield: This is a very unusual piece of equipment from 16th and 17th Century Renaissance. It is a glove with a built in buckler that also has a compartment for a lantern (hence the name: Lantern Shield), build in blades and sword catchers. So, a lantern-knife-shield-glove. Despite seeming like something from a bad fanfic, the Lantern Shield was used and useful in two very specific cases - by night watchmen on patrol, and by duelists dueling at dawn. The weapon has likely emerged back then when duelists used to wield lanterns in duels in order to blind their opponents. They even had fencing manuals where they had lanterns integrated into their training, thus allowing them to not only parry, but also, as mentioned previously, to blind their opponents. Thus the Lantern Shield appeared. From looking at it, there will be people who'd like to have something like that into their D&D games or any other fantasy pen and paper RPG. Sadly there are no rules for using it in games such as Dungeons and Dragons (alternative for it would be the Spiked Shield). Seriously, this should get more attention.
- German Dueling Shield/Two-Handed Shield: Coming Soon.
- Timbe: A buckler-type shield of Okinawan origin. The Timbe could be made from a variety of materials, but the most notable one was made from polished turtle shell.
- Ngoni Shield: A catchall term for an oval cowhide shield of the Ngoni people that could also be used for bashing enemies or hooking them off-balance before stabbing them with a killing blow. Made famous due to Zulu warfare.