The British Army Between the Wars: 1918-1939

Introduction

The period between the two World Wars — 1918 to 1939 — is one of the most fascinating and underappreciated eras in British military history. Sandwiched between the cataclysm of the Great War and the existential crisis of the Second World War, the inter-war years saw the British Army grapple with shrinking budgets, imperial policing obligations, rapid technological change, and the challenge of preparing for a conflict that many hoped would never come.

Demobilisation and Retrenchment

In November 1918, the British Army stood at approximately 3.5 million men. By 1922, it had been reduced to barely 230,000 — smaller than it had been in 1914. The demobilisation was carried out with remarkable speed but not without friction. Riots by soldiers frustrated at the slowness of their release broke out in camps at Calais, Folkestone, and elsewhere in early 1919.

The peacetime army reverted to its pre-war role as an imperial constabulary. Garrisons were maintained across the Empire — India (by far the largest commitment), Egypt, Palestine, Mesopotamia (Iraq), Aden, the Far East, and numerous smaller stations. The Army occupied the Rhineland until 1929 under the terms of the Treaty of Versailles. These commitments stretched a small army thinly across the globe.

The Ten Year Rule, first adopted in 1919 and renewed annually until 1932, assumed that Britain would not be involved in a major war for at least ten years. This policy — intended to restrain military expenditure — had a devastating effect on modernisation, equipment procurement, and the maintenance of a war reserve. When rearmament finally began in earnest after 1936, nearly two decades of underinvestment had to be made good in a matter of years.

Imperial Policing

The inter-war army was primarily employed on imperial duties. The most significant campaigns included:

• Ireland (1919-1921) — The Irish War of Independence was fought against a guerrilla enemy in an environment that anticipated many later insurgencies. The deployment of the Black and Tans and Auxiliaries remains one of the most controversial episodes in British military history.
• Mesopotamia/Iraq (1920s) — The Iraqi revolt of 1920 required substantial military force to suppress. Thereafter, the RAF assumed primary responsibility for imperial control in Iraq — an early experiment in “air policing” that replaced expensive ground garrisons with cheaper (and more controversial) air bombardment.
• Palestine (1936-1939) — The Arab Revolt required the deployment of two divisions and gave the army valuable experience in counter-insurgency that would prove relevant in subsequent decades.
• India’s North-West Frontier — The perennial frontier campaigns continued throughout the inter-war period. Operations in Waziristan, Mohmand, and the Khyber provided continuous active service experience for officers and men.

Mechanisation and Modernisation

The inter-war period saw the British Army lead the world in armoured warfare theory — and then fail to implement it. The Experimental Mechanised Force of 1927-1928 was the world’s first combined-arms armoured formation, pioneering the integration of tanks, motorised infantry, and mobile artillery. J.F.C. Fuller, Basil Liddell Hart, Percy Hobart, and other British theorists developed concepts of mobile armoured warfare that were more influential in Germany than in their own army.

The cavalry clung to the horse longer than operational logic justified — the last cavalry charge by British forces was in Palestine in 1920, yet mechanisation of cavalry regiments was not complete until the late 1930s. The conversion of hussars, lancers, and dragoons from horses to armoured cars and tanks was emotionally painful for regiments whose identity was bound up with the horse.

Infantry mechanisation was equally gradual. The Bren Gun Carrier (Universal Carrier), introduced in 1935, provided the infantry with its first tracked armoured vehicle. The adoption of the Bren light machine gun (1937) and the Boys anti-tank rifle (1937) modernised infantry firepower. But the infantry still marched on foot and relied on the bolt-action Lee-Enfield rifle — much as it had in 1914.

The Regimental System

The inter-war period was the golden age of the regimental system. Without the disruptions of total war, regiments maintained their traditions, esprit de corps, and local recruiting connections. The regimental depot was the centre of each regiment’s identity — recruits were trained there, the colours were housed there, and old soldiers returned to visit.

Regimental dress and insignia reached peak elaboration in the inter-war years. Mess dress, which had been suspended during the war, was restored and elaborated. Cap badges, collar badges, shoulder titles, and buttons were produced to exacting peacetime standards. For collectors, inter-war insignia is often of superb quality — die-struck from high-quality brass, with crisp detail and a level of finish that wartime production could never match.

Collecting Inter-War Militaria

The inter-war period produces distinctive collectables:

• General Service Medals — the GSM 1918-62 with clasps for Iraq, Palestine, North West Frontier, and other campaigns is the core inter-war medal. Named examples to specific regiments can be researched through medal rolls at The National Archives.
• India General Service Medals — the IGSM 1908-35 and IGSM 1936-39 cover frontier campaigns. Multiple-clasp medals are particularly sought after.
• Insignia — peacetime production badges and buttons in excellent quality. Inter-war patterns often show the King’s Crown (George V or George VI) and represent the last examples produced before WWII economy measures reduced standards.
• Photographs and documents — studio photographs of soldiers in immaculate peacetime uniform, often with tropical helmets and Sam Browne belts, are evocative records of the imperial army at its most polished.

Sources

• Bond, Brian. British Military Policy Between the Two World Wars. Clarendon Press, 1980.
• French, David. Raising Churchill’s Army: The British Army and the War Against Germany 1919-1945. Oxford University Press, 2000.
• Townshend, Charles. When God Made Hell: The British Invasion of Mesopotamia. Faber, 2010.
• The National Archives. WO 373 (gallantry recommendations), WO 100 and WO 329 (medal rolls).
• National Army Museum. Inter-war collections and photographic archive.

The Shadow of the Great War

Everything about the inter-war British Army was shaped by the experience of 1914-18. The officer corps was dominated by men who had served in the trenches — their experiences profoundly influenced their approach to doctrine, training, and leadership. The trauma of the Somme and Passchendaele created a deep institutional reluctance to contemplate another continental war involving mass armies.

This reluctance manifested in several ways. The Army resisted conscription planning until the very eve of war. Strategic thinking favoured imperial defence and limited liability over a continental commitment. The debate between “continentalists” (who argued Britain must be prepared to fight in Europe) and “peripheralists” (who favoured naval power and imperial strategy) consumed strategic thinking throughout the 1930s and was never fully resolved before September 1939.

The Haldane-era BEF had been a small, highly professional force designed for rapid deployment. The inter-war army inherited this model but struggled to maintain it. Pay was poor, conditions were spartan, and public attitudes towards the military — influenced by the anti-war literature of the late 1920s — were often indifferent or hostile. Recruitment was difficult, and the Army drew disproportionately from areas of high unemployment.

The Cardwell and Linked-Battalion System

The inter-war army operated under the linked-battalion system established by Cardwell in 1872 and refined by Childers in 1881. Each infantry regiment maintained two regular battalions — one serving overseas and one at home (providing a training and reinforcement base). In practice, the home battalion was often understrength, and the system creaked under the weight of imperial commitments that required more battalions overseas than the establishment could sustain.

Territorial Army battalions provided the reserve force. After the near-collapse of the Territorials in the immediate post-war period, they were reconstituted in 1920-21 and gradually rebuilt to a strength of approximately 130,000 by the mid-1930s. Their equipment was often obsolete — some TA battalions were still using Lewis guns and Vickers guns from WWI stocks — and training time was limited to annual camp and weekend drills.

Dress and Uniform

The inter-war period was the last era of elaborate peacetime military dress. Service Dress — the khaki uniform introduced in 1902 and refined through the Great War — was the standard working dress. Officers purchased their own uniforms from regimental tailors (Hawkes, Gieves, Meyer and Mortimer) and the quality was often superb. The Sam Browne belt, riding boots, and service dress cap became the iconic image of the inter-war British officer.

Full dress was restored for guards and household troops after the war and continues to this day. Other regiments retained elements of full dress for mess and ceremonial occasions. Mess dress — the evening formal uniform worn at regimental dinners — reached its most elaborate form in the inter-war years, with each regiment maintaining distinctive facings, waistcoats, and collar badges.

For collectors, inter-war uniforms are among the most desirable. The combination of peacetime tailoring quality and the romance of the imperial army creates a powerful appeal. Complete officer’s service dress with Sam Browne, cap, and accessories commands premium prices at specialist dealers and auctions.

Legacy and the Road to 1939

When war came in September 1939, the British Army was far better prepared than it had been in August 1914 in some respects — armoured doctrine had advanced, signals and radio communications were immeasurably improved, and the officer corps had absorbed the lessons of the Great War. In others, it was dangerously deficient — air defence was primitive, anti-tank weapons were inadequate, and the Territorial divisions were months from readiness. The inter-war years had been a period of making do, of preserving traditions while struggling to modernise, and the legacy was a force that was brave, professional, and experienced, but numerically and materially unequal to the challenge of a European war.