First Army (United Kingdom)

First Army (United Kingdom)
Unit name	First Army
Dates	1914–1946, 1950s–1970s
Country	United Kingdom
Branch	British Army
Type	Field army
Role	Command of multiple corps
Notable commanders	Sir Douglas Haig, Sir Henry Horne, Sir Harold Alexander

First Army (United Kingdom) First Army was a principal British field army formation that served on the Western Front in the First World War and in the Mediterranean and North-West Europe during the Second World War. It commanded multiple corps and divisions in campaigns such as the Battle of the Somme, the Hundred Days Offensive, the Tunisian Campaign, and the Northwest Europe Campaign. First Army's commanders and staff included figures prominent in British and Allied planning during the eras of Kaiser Wilhelm II, Georges Clemenceau, and Franklin D. Roosevelt.

Formation and Early History

First Army was created amid the 1914 mobilization of the British Expeditionary Force for deployment to the Western Front. Its establishment reflected prewar planning influenced by the Cardwell Reforms, the Esher Report, and lessons from the Second Boer War. Early leadership drew on officers who had served in the Egyptian Campaign, the Sudan Campaign, and at staff colleges such as the Staff College, Camberley. The army integrated formations evacuated from domestic districts including the Aldershot Command and units with battle experience from the Tirah Campaign.

First World War

Deployed to the Western Front, First Army took part in major 1916–1918 operations alongside formations of the French Army and later coordinated with the American Expeditionary Forces. During the Battle of the Somme it controlled corps that had earlier fought at Ypres and at the Battle of Neuve Chapelle. Commanders such as Sir Douglas Haig and Sir Henry Rawlinson influenced tactics that intersected with innovations by figures like John Monash and Ferdinand Foch. First Army's artillery and infantry worked with Royal Flying Corps squadrons and with tunnelling companies from the Royal Engineers in attacks near Loos and Arras. In 1917–1918 the army participated in the Passchendaele sector and in the defensive and offensive actions during the German Spring Offensive and the Allied Hundred Days Offensive, coordinating with units from the Canadian Corps, Australian Corps, and New Zealand Division.

Interwar Period and Reorganization

Following the Armistice of 11 November 1918 and the Treaty of Versailles, First Army headquarters was demobilized amid widespread reductions affecting the British Army of the Rhine and home commands such as Home Counties Division. Interwar reorganization reflected political pressures from David Lloyd George and budgetary constraints set by the Ten Year Rule, influencing the composition of field armies and the role of the War Office. Officers who had commanded at First Army served in posts within the Imperial General Staff, at the War College, and in colonial commands across the British Empire, including in India and Egypt.

Second World War

Reconstituted for operations in the Mediterranean Theatre, First Army formed part of Allied Force Headquarters during campaigns in North Africa, joining multinational efforts with the United States Army, the Free French Forces, and the British Eighth Army. It played a role in the Tunisian Campaign alongside commanders such as Harold Alexander and engaged enemy forces commanded by Erwin Rommel and Field Marshal Kesselring. Later, First Army elements were involved in planning related to the Operation Overlord and in follow-on operations in Northwest Europe cooperating with the 21st Army Group, the Canadian Army Group, and air assets of the Royal Air Force. Its staff liaised with Allied political leaders including Winston Churchill, Harry S. Truman, and representatives from Charles de Gaulle's committees.

Postwar Operations and Cold War Role

After 1945 First Army headquarters was again disbanded and elements integrated into occupation structures such as the British Army of the Rhine and the Allied Control Commission. During the early Cold War the concept of numbered armies influenced formations assigned to NATO structures including Supreme Headquarters Allied Powers Europe and national mobilization plans coordinated with the Ministry of Defence. Veterans who had served under First Army transferred expertise to institutions like the Royal Military Academy Sandhurst and to advisory roles within the Foreign Office and at the United Nations.

Commanders and Organisation

Commanders associated with First Army-era headquarters included senior officers who also served in commands such as British Expeditionary Force (World War I), Middle East Command (British Army), and the Mediterranean Allied Command. The army's structure comprised corps-level headquarters, divisions raised from territorial formations such as the Territorial Force, infantry brigades, armoured brigades equipped by Royal Tank Regiment units, artillery brigades of the Royal Artillery, and support from the Royal Engineers and Royal Army Medical Corps. Liaison with allied formations included the United States II Corps, the French XIX Corps, and multinational logistic chains tied to ports like Bizerte and Cherbourg.

Legacy and Traditions

First Army's operational history influenced British doctrine adopted in postwar manuals and expedited professional studies at institutions such as the Imperial Defence College and the Foreign and Commonwealth Office's strategic sections. Commemorations of actions involving First Army appear in memorials associated with sites like Thiepval Memorial, Beaumont-Hamel, and various battlefield cemeteries curated by the Commonwealth War Graves Commission. Regimental traditions maintained by units that served under First Army continue in lineages preserved by museums including the Imperial War Museum and collections at the National Army Museum.

Category:Field armies of the United Kingdom Category:Military units and formations established in 1914