Firearms in the context of Janissary Corps

Gunpowder is the first explosive to have been created in the world. Popularly listed as one of the "Four Great Inventions" of China, it was invented during the late Tang dynasty (9th century) while the earliest recorded chemical formula for gunpowder dates to the Song dynasty (11th century). Knowledge of gunpowder spread rapidly throughout Eurasia, possibly as a result of the Mongol conquests during the 13th century, with written formulas for it appearing in the Middle East between 1240 and 1280 in a treatise by Hasan al-Rammah, and in Europe by 1267 in the Opus Majus by Roger Bacon. It was employed in warfare to some effect from at least the 10th century in weapons such as fire arrows, bombs, and the fire lance before the appearance of the gun in the 13th century. While the fire lance was eventually supplanted by the gun, other gunpowder weapons such as rockets and fire arrows continued to see use in China, Korea, India, and this eventually led to its use in the Middle East, Europe, and Africa. Bombs too never ceased to develop and continued to progress into the modern day as grenades, mines, and other explosive implements. Gunpowder has also been used for non-military purposes such as fireworks for entertainment, or in explosives for mining and tunneling.

The evolution of guns led to the development of large artillery pieces, popularly known as bombards, during the 15th century, pioneered by states such as the Duchy of Burgundy. Firearms came to dominate early modern warfare in Europe by the 17th century. The gradual improvement of cannons firing heavier rounds for a greater impact against fortifications led to the invention of the star fort and the bastion in the Western world, where traditional city walls and castles were no longer suitable for defense. The use of gunpowder technology also spread throughout the Islamic world and to India, Korea, and Japan. The so-called Gunpowder Empires of the early modern period consisted of the Mughal Empire, Safavid Empire, and Ottoman Empire.

A janissary (UK: /ˈdʒænɪsəri/ JAN-iss-ər-ee, US: /-sɛri/ -⁠err-ee; Ottoman Turkish: یڭیچری, romanized: yeñiçeri, IPA: [jeˈŋit͡ʃeɾ̞i], lit. 'new soldier') was a member of the elite infantry units that formed the Ottoman sultan's household troops. They were the first modern standing army, and perhaps the first infantry force in the world to be equipped with firearms, adopted during the reign of Murad II (r. 1421–1444, 1446–1451). The corps was established under either Orhan or Murad I, and dismantled by Mahmud II in 1826.

Janissaries began as an elite corps made up through the devşirme system of child levy enslavement, by which Christian boys, chiefly from the Balkans, were taken, levied, subjected to forced circumcision and forced conversion to Islam, and incorporated into the Ottoman army. They became famed for internal cohesion cemented by strict discipline and order. Unlike typical slaves, they were paid regular salaries. Forbidden to marry before the age of 40 or engage in trade, their complete loyalty to the Ottoman sultan was expected. By the 17th century, due to a dramatic increase in the size of the Ottoman standing army, the corps' initially strict recruitment policy was relaxed. Civilians bought their way into it in order to benefit from the improved socio-economic status it conferred upon them. Consequently, the corps gradually lost its military character, undergoing a process that has been described as "civilianization".

"Gunpowder empires", or "Islamic gunpowder empires", is a term coined by the American historians Marshall G. S. Hodgson and William H. McNeill to describe three early modern Muslim empires: the Ottoman Empire, Safavid Empire and the Mughal Empire, which flourished between the mid-16th and early 18th centuries.

McNeill focused on the history of gunpowder use across multiple civilizations in East Asia, Europe, and India in his 1993 work The Age of Gunpowder Empires. The gunpowder empires conquered vast amounts of territory with the use and deployment of newly invented firearms, especially cannon and small arms; together they stretched from Central Europe and North Africa in the west to Bengal and Arakan in the east. In the case of Europe, the introduction of gunpowder weapons also prompted changes such as the rise of centralised monarchical states. As a result, the three empires were among the most stable of the early modern period, leading to commercial expansion, cultural patronage, and the consolidation of political and legal institutions.

A sight or sighting device is any device used to assist in precise visual alignment (i.e. aiming) of weapons, surveying instruments, aircraft equipment, optical illumination equipment or larger optical instruments with the intended target. Sights can be a simple set or system of physical markers that serve as visual references for directly aligning the user's line of sight with the target (such as iron sights on firearms), or optical instruments that provide an optically enhanced—often magnified—target image aligned in the same focus with an aiming point (e.g. telescopic, reflector and holographic sights). There are also sights that actively project an illuminated point of aim (a.k.a. "hot spot") onto the target itself so it can be observed by anyone with a direct view, such as laser sights and infrared illuminators on some night vision devices, as well as augmented or even virtual reality-enabled digital cameras ("smart scopes") with software algorithms that produce digitally enhanced target images.

The siege of De'an (德安之戰) was fought as part of the Jin–Song Wars of China in 1132, during the Jin invasion of Hubei and Shaanxi. The battle between the besiegers, a group of rebels led by Li Heng and the Song Chinese defenders is important in global history as the first recorded instance of the fire lance, an early ancestor of firearms, being used in battle.

A smoothbore weapon is one that has a barrel without rifling. Smoothbores range from handheld firearms to powerful tank guns and large artillery mortars. Some examples of smoothbore weapons are muskets, blunderbusses, and flintlock pistols. The opposite of smoothbore is rifling.

On December 14, 2012, a mass shooting occurred at Sandy Hook Elementary School in Newtown, Connecticut, United States. The perpetrator, 20-year-old Adam Lanza, shot and killed 26 people. The victims were 20 children between six and seven years old, and six adult staff members. Earlier that day, before driving to the school, Lanza fatally shot his mother at their Newtown home. As first responders arrived at the school, Lanza killed himself with a gunshot to the head.

The incident is the deadliest mass shooting in Connecticut history and the deadliest at an elementary school in U.S. history. The shooting prompted renewed debate about gun control in the United States, including proposals to make the background check system universal, and for new federal and state gun legislation banning the sale and manufacture of certain types of semi-automatic firearms and magazines which can hold more than ten rounds of ammunition.

Toqui (or Toki) (Mapudungun for axe or axe-bearer) is a title conferred by the Mapuche (an indigenous Chilean and Argentinian people) on those chosen as leaders during times of war. The toqui is chosen in an assembly or parliament (coyag) of the chieftains (loncos) of various clans (Rehues) or confederation of clans (Aillarehues), allied during the war at hand. The toqui commanded strict obedience of all the warriors and their loncos during the war, would organize them into units and appoint leaders over them. This command would continue until the toqui was killed, abdicated (Cayancaru), was deposed in another parliament (as in the case of Lincoyan, for poor leadership), or upon completion of the war for which he was chosen.

Some of the more famous Toqui in the Arauco War with the Spanish introduced tactical innovations. For example, Lautaro introduced infantry tactics to defeat horsemen. Lemucaguin was the first Toqui to use firearms and artillery in battle. Nongoniel was the first Toqui to use cavalry with the Mapuche army. Cadeguala was the first to successfully use Mapuche cavalry to defeat Spanish cavalry in battle. Anganamón was the first to mount his infantry to keep up with his fast-moving cavalry. Lientur pioneered the tactic of numerous and rapid malóns into Spanish territory.

The Royal Armouries is the United Kingdom's national collection of arms and armour. Once an important part of England's military organization, it became the United Kingdom's oldest museum, and one of the oldest museums in the world. It is also one of the largest collections of arms and armour in the world, comprising the UK's National Collection of Arms and Armour, National Artillery Collection, and National Firearms Collection. Originally housed in the Tower of London from the 15th century, today the collection is split across three sites: the Tower, the Royal Armouries Museum in Leeds, and Fort Nelson near Portsmouth.

From 2004 to 2015, a limited selection of items was also on display in Louisville, Kentucky, in the United States, in cooperation with the Frazier History Museum.

A close order formation is a military tactical formation in which soldiers are close together and regularly arranged for the tactical concentration of force. It was used by heavy infantry in ancient warfare, as the basis for shield wall and phalanx tactics, to multiply their effective weight of arms by their weight of numbers. In the Late Middle Ages, Swiss pikemen and German Landsknechts used close order formations that were similar to ancient phalanxes.

Around the American Civil War (1861–1865), such organizations of soldiers became uncommon since improvements in firearms and artillery had made any such dense formation increasingly hazardous and less effective. The technological concentration of increased firepower to fewer soldiers had rendered the close order formation obsolete by the end of the 19th century. Modern infantry now use skirmish order, which is effectively the opposite of close order.

An arquebus (/ˈɑːrk(w)əbəs/ AR-k(w)ə-bəs) is a form of long gun that appeared in Europe and the Ottoman Empire during the 15th century. An infantryman armed with an arquebus is called an arquebusier.

The term arquebus was applied to many different forms of firearms from the 15th to 17th centuries, but it originally referred to "a hand-gun with a hook-like projection or lug on its under surface, useful for steadying it against battlements or other objects when firing". These "hook guns" were in their earliest forms defensive weapons mounted on German city walls in the early 15th century. The addition of a shoulder stock, priming pan, and matchlock mechanism in the late 15th century turned the arquebus into a handheld firearm and also the first firearm equipped with a trigger.

In firearms terminology, an action is the functional mechanism of a breechloading firearm that handles (loads, locks, fires, extracts, and ejects) the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock (e.g. matchlock, wheellock, flintlock, and caplock).

Actions can be categorized in several ways, including single action versus double action, break action versus lever-action, pump-action, bolt-action, among many other types. The term action can also include short, long, and magnum if it is in reference to the length of the rifle's receiver and the length of the bolt. The short action rifle usually can accommodate a cartridge length of 2.8 in (71 mm) or smaller. The long action rifle can accommodate a cartridge of 3.34 in (85 mm), and the magnum action rifle can accommodate cartridges of 3.6 in (91 mm).