Lord General Thomas Fairfax, the first commander of the New Model Army
English Civil War, England never had a
standing army with professional officers and careerist corporals and sergeants. It relied on militia organized by local officials, or private forces mobilized by the nobility, or on hired mercenaries from Europe.
 From the later Middle Ages until the English Civil War, when a foreign expeditionary force was needed, such as the one that
Henry V of England took to France and that fought at the
Battle of Agincourt (1415), the army, a professional one, was raised for the duration of the expedition.
During the English Civil War, the members of the
Long Parliament realised that the use of county militia organised into regional associations (such as the
Eastern Association), often commanded by local members of parliament (both from the House of Commons and the House of Lords), while more than able to hold their own in the regions which Parliamentarians controlled, were unlikely to win the war. So Parliament initiated two actions. The
Self-denying Ordinance, with the notable exception of
Oliver Cromwell, forbade members of parliament from serving as officers in the Parliamentary armies. This created a distinction between the civilians in Parliament, who tended to be Presbyterian and conciliatory to the Royalists in nature, and a corps of professional officers, who tended to Independent politics, to whom they reported. The second action was legislation for the creation of a Parliamentary-funded army, commanded by Lord General
Thomas Fairfax, which became known as the
New Model Army (originally new-modelled Army).
While this proved to be a war winning formula, the New Model Army, being organized and politically active, went on to dominate the politics of the
Interregnum and by 1660 was widely disliked. The New Model Army was paid off and disbanded at the
Restoration of the monarchy in 1660. For many decades the excesses of the New Model Army under
the Protectorate of Oliver Cromwell was a horror story and the Whig element recoiled from allowing a standing army.
 The militia acts of 1661 and 1662 prevented local authorities from calling up militia and oppressing their own local opponents. Calling up the militia was possible only if the king and local elites agreed to do so.
Charles II and his
Cavalier supporters favoured a new army under royal control; and immediately after the Restoration began working on its establishment.
 The first
English Army regiments, including elements of the disbanded
New Model Army, were formed between November 1660 and January 1661
 and became a standing military force for Britain (financed by
Royal Scots and
Irish Armies were financed by the parliaments of
 Parliamentary control was established by the
Bill of Rights 1689 and
Claim of Right Act 1689, although the monarch continued to influence aspects of army administration until at least the end of the nineteenth century.
After the Restoration Charles II pulled together four regiments of infantry and cavalry, calling them his guards, at a cost of £122,000 from his general budget. This became the foundation of the permanent English Army. By 1685 it had grown to 7,500 soldiers in marching regiments, and 1,400 men permanently stationed in garrisons. A
rebellion in 1685 allowed
James II to raise the forces to 20,000 men. There were 37,000 in 1678, when England played a role in the closing stage of the Franco-Dutch War. After
Mary's accession to the throne England involved itself in the
War of the Grand Alliance, primarily to prevent a French invasion restoring James II (Mary's father).
 In 1689, William III expanded the army to 74,000, and then to 94,000 in 1694. Parliament was very nervous, and reduced the cadre to 7000 in 1697. Scotland and Ireland had theoretically separate military establishments, but they were unofficially merged with the English force.
By the time of the 1707
Acts of Union, many regiments of the English and Scottish armies were combined under one operational command and stationed in the Netherlands for the
War of the Spanish Succession. Although all the regiments were now part of the new British military establishment,
 they remained under the old operational-command structure and retained much of the institutional ethos, customs and traditions of the standing armies created shortly after the
restoration of the monarchy 47 years earlier. The order of seniority of the most-senior British Army line regiments is based on that of the English army. Although technically the Scots
was raised in 1633 and is the oldest Regiment of the Line,
 Scottish and Irish regiments were only allowed to take a rank in the English army on the date of their arrival in England (or the date when they were first placed on the English establishment). In 1694, a board of general officers was convened to decide the rank of English, Irish and Scots regiments serving in the Netherlands; the regiment which became known as the
Scots Greys were designated the 4th Dragoons because there were three English regiments raised prior to 1688, when the Scots Greys were first placed in the English establishment. In 1713, when a new board of general officers was convened to decide the rank of several regiments, the seniority of the Scots Greys was reassessed and based on their June 1685 entry into England. At that time there was only one English regiment of dragoons, and the Scots Greys eventually received the British Army rank of 2nd Dragoons.
British Empire (1700–1914)
After 1700 British continental policy was to contain expansion by competing powers such as France and Spain. Although Spain was the dominant global power during the previous two centuries and the chief threat to England's early transatlantic ambitions, its influence was now waning. The territorial ambitions of the French, however, led to the War of the Spanish Succession
 and the
Royal Navy is widely regarded as vital to the rise of the
British Empire, the British Army played an important role in the formation of colonies,
dominions in the Americas, Africa, Asia, India and
 British soldiers captured strategically-important territories, and the army was involved in wars to secure the empire's borders and support friendly governments. Among these actions were the Seven Years' War,
American Revolutionary War,
Second Opium Wars,
New Zealand Wars,
Sepoy Rebellion of 1857,
second Boer Wars,
Irish War of Independence,
 interventions in
Afghanistan (intended to maintain a
buffer state between British India and the
 and the
Crimean War (to keep the Russian Empire at a safe distance by aiding Turkey).
 Like the
English Army, the British Army fought the kingdoms of Spain, France (including the Empire of France) and the Netherlands for supremacy in North America and the
West Indies. With native and provincial assistance, the army conquered
New France in the
North American theatre of the
Seven Years' War
 and suppressed a
Native American uprising in
 The British Army was defeated in the American Revolutionary War, losing the
Thirteen Colonies but retaining
The Canadas and
The Maritimes as
British North America.
The British Army was heavily involved in the
Napoleonic Wars, participating in a number of campaigns in Europe (including continuous deployment in the
Peninsular War), the
Caribbean, North Africa and
North America. The war between the British and the
First French Empire of
Napoleon Bonaparte stretched around the world; at its peak in 1813, the regular army contained over 250,000 men. A coalition of Anglo-Dutch and Prussian armies under the
Duke of Wellington and
Field Marshal von Blücher finally defeated Napoleon at
Waterloo in 1815.
The English were involved politically and militarily in Ireland since receiving the
Lordship of Ireland from the pope in 1171. The campaign of English republican Protector
Oliver Cromwell involved uncompromising treatment of the Irish towns (most notably
Wexford) which supported the Royalists during the
English Civil War. The English Army (and the subsequent British Army) remained in Ireland primarily to suppress Irish revolts or disorder. In addition to its conflict with Irish nationalists, it was faced with the prospect of battling Anglo-Irish and
Ulster Scots in Ireland who were angered by unfavourable taxation of Irish produce imported into Britain. With other Irish groups, they raised a volunteer army and threatened to emulate the American colonists if their conditions were not met. Learning from their experience in America, the British government sought a political solution. The British Army fought Irish rebels—Protestant and Catholic—primarily in
United Irishmen) in the
In addition to battling the armies of other European empires (and its former colonies, the United States, in the War of 1812),
 the British Army fought the Chinese in the first and second Opium Wars
 and the Boxer Rebellion,
Māori tribes in the first of the New Zealand Wars,
 Nawab Shiraj-ud-Daula's forces and
British East India Company mutineers in the Sepoy Rebellion of 1857,
 the Boers in the first and second Boer Wars,
Fenians in Canada during the
Irish separatists in the
 The increasing demands of imperial expansion and the inadequacy and inefficiency of the underfunded British Army,
Volunteer Force after the Napoleonic Wars led to the late-19th-century
Childers Reforms, which gave the army its modern shape and redefined its
 The 1907
Haldane Reforms created the
Territorial Force as the army's volunteer reserve component, merging and reorganising the Volunteer Force, Militia and Yeomanry.
World Wars (1914–1945)
British World War I
Mark I tank
; the guidance wheels behind the main body were later scrapped as unnecessary. Armoured vehicles of the era required considerable infantry and artillery support. (Photo by
Infantrymen of the
carts returning from the trenches near Albert, France in September 1916. In the background is a line of supply lorries.
Great Britain has been challenged by other powers, primarily the
German Empire and the
Third Reich during the 20th century. A century earlier it vied with Napoleonic France for global pre-eminence, and
Hannoverian Britain's natural allies were the kingdoms and principalities of
northern Germany. By the middle of the 19th century, Britain and France were allies in preventing Russia's appropriation of the
Ottoman Empire (although the fear of French invasion led shortly afterwards to the creation of the Volunteer Force. By the first decade of the 20th century, the United Kingdom was allied with France (by the
Entente Cordiale) and Russia (which had a secret agreement with France for mutual support in a war against the
Prussian-led German Empire and the
When the First World War broke out in August 1914 the British Army sent the
British Expeditionary Force (BEF), consisting mainly of
regular army troops, to
France and Belgium.
 The fighting bogged down into static
trench warfare for the remainder of the war. In 1915 the army created the
Mediterranean Expeditionary Force to invade the
Ottoman Empire via
Gallipoli, an unsuccessful attempt to capture
Constantinople and secure a sea route to
World War I was the most devastating in
British military history, with nearly 800,000 men killed and over two million wounded. Early in the war, the BEF was virtually destroyed and was replaced first by
volunteers and then a
conscript force. Major battles included those at
the Somme and
 Advances in technology saw the advent of the
 (and the creation of the
Royal Tank Regiment) and advances in aircraft design (including the creation of the
Royal Flying Corps) which would be decisive in future battles.
 Trench warfare dominated Western Front strategy for most of the war, and the use of
chemical weapons (disabling and poison gases) added to the devastation.
Second World War broke out in September 1939 with the Russian and
invasion of Poland.
 British assurances to the Poles led the British Empire to declare war on
Germany. As in the First World War, a relatively-small
BEF was sent to France
 and hastily evacuated from
Dunkirk as the German forces
swept through the Low Countries and across France in May 1940.
After the US entered the war and the British Army recovered from its earlier defeats, it defeated the Germans and Italians at the
Second Battle of El Alamein in
North Africa in 1942–1943 and helped drive them from Africa. It then fought through
Italy and, with the help of American, Canadian, Australian, New Zealand, Indian and Free French forces,
 took part in the
D-Day invasion of Normandy on 6 June 1944; nearly half the Allied soldiers were British. In the
Far East, the British Army rallied against the Japanese in the
Burma Campaign and regained the British Far Eastern colonial possessions.
Postcolonial era (1945–2000)
After the Second World War the British Army was significantly reduced in size, although
National Service continued until 1960.
 This period saw
decolonisation begin with the
independence of India and Pakistan, followed by the independence of British colonies in Africa and Asia. Although the British Army was a major participant in
Korea in the early 1950s
Suez in 1956,
 during this period Britain's role in world events was reduced and the army was downsized.
British Army of the Rhine, consisting of
I (BR) Corps, remained in Germany as a bulwark against Soviet invasion.
Cold War continued, with significant technological advances in warfare, and the army saw the introduction of new weapons systems.
 Despite the decline of the British Empire, the army was engaged in
 In 1982, the British Army and the
Royal Marines helped liberate the
Falkland Islands during the
conflict with Argentina after that country's invasion of the British territory.
In the three decades following 1969, the army was heavily deployed in
Operation Banner to support the
Royal Ulster Constabulary (later the
Police Service of Northern Ireland) in their conflict with republican paramilitary groups.
 The locally recruited
Ulster Defence Regiment was formed, becoming home-service battalions of the
Royal Irish Regiment in 1992 before it was disbanded in 2006. Over 700 soldiers were killed during
the Troubles. Following the 1994–1996
IRA ceasefires and since 1997, demilitarisation has been part of the peace process and the military presence has been reduced.
 On 25 June 2007 the 2nd Battalion of the
Princess of Wales's Royal Regiment left the army complex in
County Armagh, ending the longest operation in British Army history.
Persian Gulf War
The British Army contributed 50,000 troops to the coalition which fought
Iraq in the
Persian Gulf War,
 and British forces controlled
Kuwait after its liberation. Forty-seven British military personnel died during the war.
The army was deployed to
Yugoslavia in 1992. Initially part of the
United Nations Protection Force,
 in 1995 its command was transferred to the
Implementation Force (IFOR) and then to the
Stabilisation Force in Bosnia and Herzegovina (SFOR);
 the commitment rose to over 10,000 troops. In 1999, British forces under SFOR command were sent to
Kosovo and the contingent increased to 19,000 troops.
 Between early 1993 and June 2010, 72 British military personnel died during operations in the former Yugoslavian countries of Bosnia, Kosovo and Macedonia.
Although there have been permanent garrisons in Northern Ireland throughout its history, the British Army was deployed as a peacekeeping force from 1969 to 2007 in
Operation Banner. Initially, this was (in the wake of
unionist attacks on nationalist communities in
 to prevent further loyalist attacks on Catholic communities; it developed into support of the
Royal Ulster Constabulary (RUC) and its successor, the
Police Service of Northern Ireland (PSNI) against the
Provisional Irish Republican Army (PIRA). Under the 1998
Good Friday Agreement, there was a gradual reduction in the number of soldiers deployed.
 In 2005, after the PIRA declared a ceasefire, the British Army dismantled posts, withdrew many troops and restored troop levels to those of a peace-time garrison.
Operation Banner ended at midnight on 31 July 2007 after about 38 years of continuous deployment, the longest in British Army history.
 According to an internal document released in 2007, the British Army had failed to defeat the IRA but made it impossible for them to win by violence. Operation Helvetic replaced Operation Banner in 2007, maintaining fewer service personnel in a more-benign environment.
 From 1971 to 1997, a total of 763 British military personnel were killed during the Troubles.
 About 300 deaths during the conflict were attributed to the British Army, including paramilitary troops and civilians.
Recent history (2000–present)
War in Afghanistan
In November 2001, as part of
Operation Enduring Freedom with the United States, the United Kingdom invaded
Afghanistan to topple the
3rd Division were deployed in
Kabul to assist in the liberation of the capital and defeat Taliban forces in the mountains. In 2006 the British Army began concentrating on fighting Taliban forces and bringing security to
Helmand Province, with around 9,500 British troops (including marines, airmen and sailors) deployed at its peak
—the second-largest force after that of the US.
 In December 2012 Prime Minister
David Cameron announced that the combat mission would end in 2014, and troop numbers gradually fell as the
Afghan National Army took over the brunt of the fighting. Between 2001 and 26 April 2014 a total of 453 British military personnel died in Afghan operations.
 Operation Herrick ended with the handover of
Camp Bastion on 26 October 2014,
 but the British Army maintains a deployment in Afghanistan as part of
In 2003 the United Kingdom was a major contributor to the
invasion of Iraq, sending a force of over 46,000 military personnel. The British Army controlled southern Iraq, maintained a peace-keeping presence in
 All British troops were withdrawn from Iraq by 30 April 2009, after the Iraqi government refused to extend their mandate.
 One hundred seventy-nine British military personnel died in Iraqi operations.
British Armed Forces returned to Iraq in 2014 as part of
Operation Shader to counter the
Islamic State (ISIL).
UK Operations/Military Aid to the Civil Authorities
The British Army maintains a standing liability to support the civil authorities in certain circumstances, usually in either niche capabilities (e.g. explosive ordance removal) or in general support of the civil authorities when their capacity is exceeded.
 In recent years this has been seen as Army personnel supporting the civil authorities in the face of the
2001 United Kingdom foot-and-mouth outbreak, the 2002 Firefighters strike, widespread flooding in 2005, 2007, 2009, 2013 and 2014 and most recently supporting the security services on
Operation Temperer following the
2017 Manchester Arena bombing.