Line infantry in the context of "King's Own Scottish Borderers"

Infantry, or infantryman are a type of soldier who specialize in ground combat, typically fighting dismounted. Historically the term was used to describe foot soldiers, i.e. those who march and fight on foot. In modern usage, the term broadly encompasses a wide variety of subspecialties, including light infantry, irregular infantry, heavy infantry, mountain infantry, motorized infantry, mechanized infantry, airborne infantry, air assault infantry, and naval infantry. Other subtypes of infantry, such as line infantry and mounted infantry, were once commonplace but fell out of favor in the 19th century with the invention of more accurate and powerful weapons.

Light infantry refers to certain types of lightly equipped infantry throughout history. They have a more mobile or fluid function than other types of infantry, such as heavy infantry or line infantry. Historically, light infantry often fought as scouts, raiders, and skirmishers. These are loose formations that fight ahead of the main army to harass, delay, disrupt supply lines, engage the enemy's own skirmishing forces, and generally "soften up" an enemy before the main battle. Light infantrymen were also often responsible for screening the main body of a military formation.

Following World War II, the term "light infantry" has evolved to include rapid-deployment units (including commando and airborne units) that emphasize speed and mobility over armor and firepower. Some units or battalions that historically held a skirmishing role retain their designation "light infantry" for the sake of tradition.

Heavy infantry consisted of heavily armed and armoured infantrymen who were trained to mount frontal assaults and/or anchor the defensive center of a battle line. This differentiated them from light infantry who were relatively mobile and lightly armoured skirmisher troops intended for screening, scouting, and other tactical roles unsuited to soldiers carrying heavier loads. Heavy infantry typically made use of dense battlefield formations, such as shield wall or phalanx, multiplying their effective weight of arms with force concentration.

Heavy infantry were critical to many ancient armies, which first attested by the Sumerians in the Stele of the Vultures. It was also used by rival Assyrian and Persian Sparabara, then by Greek hoplites, Macedonian phalangites, and Roman legionaries. After the fall of Rome, heavy infantry declined in Europe but returned to dominance in the Late Middle Ages with Swiss pikemen and German Landsknechts. With the rise of firearms during early modern warfare, dense formations became increasingly infeasible, and heavy armours were either ineffective or too cumbersome to be tactically useful. By the early 18th century, heavy infantry were replaced by line infantry armed with muskets and bayonets and wearing little to no armour.

The Royal Scots Fusiliers was a line infantry regiment of the British Army that existed from 1678 until 1959 when it was amalgamated with the Highland Light Infantry (City of Glasgow Regiment) to form the Royal Highland Fusiliers (Princess Margaret's Own Glasgow and Ayrshire Regiment) which was later itself merged with the Royal Scots, King's Own Scottish Borderers, the Black Watch (Royal Highland Regiment), the Argyll and Sutherland Highlanders and the Highlanders (Seaforth, Gordons and Camerons) to form a new large regiment, the Royal Regiment of Scotland.

The 52nd (Oxfordshire) Regiment of Foot was a light infantry regiment of the British Army throughout much of the 18th and 19th centuries. The regiment first saw active service during the American War of Independence, and were posted to India during the Anglo-Mysore Wars. During the Napoleonic Wars, the 52nd were part of the Light Division, and were present at most major battles of the Peninsula campaign, becoming one of the most celebrated regiments, described by Sir William Napier as "a regiment never surpassed in arms since arms werefirst borne by men". They had the largest British battalion at Waterloo, 1815, where they formed part of the final charge against Napoleon's Imperial Guard. They were also involved in various campaigns in India.

The regiment was raised as a line regiment in 1755 and numbered as the "54th Foot"; they were renumbered as the "52nd Regiment of Foot" in 1757. In 1781, the regional designation "52nd (Oxfordshire) Regiment of Foot" was given and in 1803 the regiment was designated "Light Infantry". In 1881, the regiment was merged with the 43rd (Monmouthshire) Regiment of Foot to become the regiment later known as the Oxfordshire and Buckinghamshire Light Infantry.

The Gordon Highlanders was a line infantry regiment of the British Army that existed for 113 years, from 1881 until 1994, when it was amalgamated with The Queen's Own Highlanders (Seaforth and Camerons) to form The Highlanders (Seaforth, Gordons and Camerons). Although the 'Gordon Highlanders' had existed as the 92nd (Gordon Highlanders) Regiment of Foot since 1794, the actual 'Gordon Highlanders Regiment' was formed in 1881 by amalgamation of the 75th (Stirlingshire) Regiment of Foot and 92nd (Gordon Highlanders) Regiment of Foot.

The Manchester Regiment was a line infantry regiment of the British Army in existence from 1881 until 1958. The regiment was created during the 1881 Childers Reforms by the amalgamation of the 63rd (West Suffolk) Regiment of Foot and the 96th Regiment of Foot as the 1st and 2nd battalions; the 6th Royal Lancashire Militia became the 3rd (Reserve) and 4th (Extra Reserve) battalions and the Volunteer battalions became the 5th, 6th, 7th, 8th, 9th and 10th battalions.

After distinguished service in both the First and the Second World Wars, the Manchester Regiment was amalgamated with the King's Regiment (Liverpool) in 1958, to form the King's Regiment (Manchester and Liverpool), which was, in 2006, amalgamated with the King's Own Royal Border Regiment and the Queen's Lancashire Regiment to form the present Duke of Lancaster's Regiment (King's, Lancashire and Border).