Experimental Mechanized Force

The Experimental Mechanized Force (EMF) was a brigade-sized formation of the British Army. It was officially formed on 1 May 1927 to investigate and develop the techniques and equipment required for armoured warfare and was the first armoured formation of its kind in the world. It was renamed the Armoured Force the following year. The Royal Air Force (RAF) took part in the exercises and demonstrated the value of ground–air co-operation.

For two years the EMF participated in exercises which demonstrated the capabilities of mechanised forces against traditionally organised and trained infantry and cavalry. The force was controversial in the army and was disbanded in February 1929. The EMF and AF were followed by experiments with a Tank Brigade in 1931, which had three mixed battalions of medium and light tanks and a battalion of Carden Loyd machine-gun carriers for reconnaissance.

In the aftermath of the First World War, several theorists sought ways to avoid a repetition of trench warfare, despite the war of movement from August to December 1914 costing the French c. 850,000 casualties and the Germans c. 670,000. The trench warfare that followed had been less costly in men but attrition warfare was indecisive; limited objective attacks, under an umbrella of massed artillery-fire, could succeed but only at the cost of unlimited duration. In 1918, fighter-bombers had been attached to the Tank Corps and bombed and machine-gunned positions blocking the advance. The weight of air attack had not been sufficient to overcome German resistance and the Tank Corps had still needed to pause until artillery caught up with the advance. Lieutenant-Colonel Percy Hobart transferred to the Tank Corps in 1923 and became something of an armoured warfare theorist, anticipating that faster tanks, self-propelled guns and much more support from RAF bombers, would allow an advance to move beyond the range of artillery.

Major-General George Lindsay had been in command of armoured cars in Iraq and seen the effect of air support, which left him with an interest in armoured operations. Lindsay thought that the war of the future would be "the Mechanised force on the ground working with the Mechanised force in the air". Trafford Leigh-Mallory, commander of the School of Army Co-operation from 1927 to 1930, promoted the new thinking. Colonel J. F. C. Fuller, Chief of Staff of the Tank Corps during the First World War and Chief instructor at the Staff College, Camberley in the 1920s, proposed an all-tank force, which would operate independently against enemy headquarters and lines of communication. Basil Liddell Hart, a retired officer, journalist and writer on military theory, advocated mechanised forces of all arms, able to carry out operations of war other than the all-out offensive. Major Giffard LeQuesne Martel, at the Experimental Bridging Establishment, a former staff officer to Fuller, designed armoured vehicles as a sideline and proposed that tanks should be subordinated to infantry formations, while many cavalry officers maintained that the horse still had a part to play on a modern battlefield, despite the evidence of Western Front in the First World War.

During the early 1920s, Japan had been considered the most likely military threat to the British Empire. Britain signed the Locarno Treaties in 1925 in accepting a responsibility with France, Germany and Belgium, militarily to intervene if one power attacked any of the others but no military forces were committed by the guarantors to enforce the treaties and their language was deliberately vague. The size of the British Empire made it difficult for the Army to plan equipment and training, since it might have to fight in diverse terrains and climates needing different types of equipment and organisation. The Cardwell Reforms of 1868–1874 had linked the metropolitan army battalions with those on overseas service but this tended to reduce British-based units to training and reinforcement cadres.

In September 1925 the army held its biggest exercise since 1914, part of which was to test new thinking on mechanised warfare. Three infantry divisions, one cavalry brigade and a tank battalion under the command of General Philip Chetwode exercised against an infantry division, two cavalry brigades and a tank brigade commanded by General Alexander Godley. On day 1, Godley formed a mobile force with the cavalry brigades, a motorised infantry brigade and artillery to attack part of the Chetwode force. The infantry disembarked from their lorries 7–10 mi (11–16 km) from their jumping-off points and took too long to arrive. The cavalry horses, also carried on lorries, got mixed up with the infantry transport. On day 3, Chetwode sent his tank battalion on a 30 mi (48 km) outflanking manoeuvre but his infantry divisions failed to pin down Godley's units which were easily able to retreat. The exercises showed that the British had much of the equipment necessary for mechanised and armoured warfare but not the theoretical framework to make them effective.

The Secretary of State for War, Sir Laming Worthington-Evans announced in March 1926 the formation of an experimental all-arms force. In February 1926, General George Milne, the General Officer Commanding (GOC) Eastern Command became the Chief of the Imperial General Staff (CIGS). Milne was suspicious of German intentions, circulated reports on German military potential and began to plan an army capable of resisting German aggression, despite post-war cuts in the Army Estimates. Continental warfare would need expensive equipment of little use in other parts of the world, where British commitments had increased since 1914. Following vacillation by the War Office and pressure from Fuller and Lindsay, the Inspector of the Royal Tank Corps, Milne arranged for the formation of the Experimental Mechanized Force in May 1927. Milne was already inclined against the pure tank theorists and organised the force as a balanced, all-arms command, which amounted to a prototype armoured division, as far as resources allowed.

Fuller was considered for appointment as commander of the force, combined with command of the 7th Infantry Brigade (Brigadier Robert Collins) and the administrative responsibilities connected with the garrison of Tidworth Camp. In what became known as the Tidworth Affair, Fuller turned down the appointment and resigned from the Army, because the War Office refused to allot extra staff to assist him. Fuller believed he would be unable to devote himself to the force, its methods and tactics. Liddell Hart wrote an article in the 22 April edition of The Daily Telegraph alleging that the Army was reneging on its commitment to assemble an experimental force. The article galvanised the Army into action and a public commitment to the force. Collins, a light infantry man, was appointed to command the Experimental Force in April 1927. The Experimental Force was established on 1 May 1927 at Tidworth Camp on Salisbury Plain; after unit training with the new equipment that summer, training of the force as a unit began on 19 August.