An order of battle is a list of the elements of a military formation that are organised within a hierarchical command structure. It can provide information on the strength of that formation and the equipment used. An order of battle is not necessarily a set structure and it can change depending on tactical or strategic developments or the evolution of military doctrine. For example, a division could be radically altered from one campaign to another through the adding or removing of sub-units but retain its identity and history. The size of a division can dramatically vary as a result of the forces assigned and the doctrine employed at that time.

The 1st Armoured Division of the British Army was formed in 1937 as the Mobile Division and renamed the 1st Armoured Division in April 1939. The division was dispatched with 257 tanks to fight in the Battle of France. After several costly engagements and the collapse of the Allied effort, it was forced to retreat back to the UK with only 13 remaining tanks. In late 1941, the division was sent to reinforce the British effort in North Africa with 184 tanks. It then fought in all the major engagements of the Western Desert campaign during 1942 from defeat in the Battle of Gazala to victory in the Second Battle of El Alamein. It assisted in the chase of the Axis powers across North Africa into Tunisia, culminating with the Axis' overall defeat on the continent. In the aftermath of the Tunisian campaign, the division remained in Africa until 1944, when it was transferred to Italy. Its final battles were against the German Gothic Line during the Italian campaign. The division was broken up in October 1944 to provide reinforcements for other active formations due to a personnel shortage in the British Army, and officially disbanded in early 1945.

Background The Mobile Division was formed in November 1937, and renamed the 1st Armoured Division in April 1939. Prior to the outbreak of the Second World War, doctrine called for such a division to be composed of two armoured brigades—each with three armoured regiments—and a support group. The support group included all required supporting arms the division would need: infantry, engineers, artillery, and anti-tank and anti-aircraft guns. At full strength, the support group would have sixteen 25-pounder field gun-howitzers, twenty-four 2-pounder anti-tank gun, and twenty-four Bofors anti-aircraft guns. On paper, the division would contain 108 light tanks, 159 light cruisers, 58 heavy cruisers, and 24 close-support tanks, and have 9,442 personnel. This basic organisation changed on numerous occasions during the war, although the actual implementation could be delayed due to several factors.

British forces defined light tanks as reconnaissance vehicles, which were armed with machine guns. Cruiser tanks were swiftly moving, more heavily armoured, and equipped with machine guns and an anti-tank gun. The cruiser tank's role was to engage and destroy enemy armoured forces. Its main weapon, a 2-pounder anti-tank gun, was supplied only with armour-piercing rounds, meaning cruiser tanks were ineffective against entrenched infantry or suppressing hostile artillery. The A9 is an example of a light cruiser while the A10 provides an example of a heavy cruiser. The light and heavy definitions arose in 1938, to differentiate between cruisers that were thinly armoured and their better armoured variants (for example, the A9 frontal armour was only thick compared to the thickness of the A10). Rather than being fitted with an anti-tank gun, close-support cruiser tanks were equipped with a howitzer for firing smoke and high-explosive rounds, and were not intended to fight other tanks.

From formation through to the outbreak of the Second World War On formation, in November 1937, the division was headquartered at Andover, Hampshire, on the edge of Salisbury Plain and was assigned to Southern Command. Two of its brigades were located around the plain: the 2nd Cavalry Brigade at Tidworth Camp and the 1st Tank Brigade at Perham Down. While the 1st Cavalry Brigade was technically part of the division, it was located at Aldershot under the command of Aldershot Command until late 1938., ,

It was intended for the division to have 620 armoured fighting vehicles, although did not reach this strength during the early years of its existence. As best they could be, the cavalry regiments were outfitted with the Light Tank Mk VI while the tank brigade contained Vickers Medium Mark IIs. Due to the lack of tanks, trucks were used to simulate their existence for training purposes. It was not until December 1938 that the first delivery of A13 cruiser tanks were made, followed by A9s in January 1939. In April 1939, several nomenclature changes took place. The Mobile Division was renamed the 1st Armoured Division, the cavalry brigades were retitled as light armoured brigades, and the tank brigade became the heavy armoured brigade. Likewise, on 4 April 1939, the Royal Armoured Corps was formed to command all mechanised cavalry and the battalions of the Royal Tank Corps. The latter was renamed the Royal Tank Regiment and its nomenclature colloquially changed; each unit dropped the word battalion from its title, although this was not officially adopted until September 1945., and

November 1937– July 1938

Mobile Division

1st Cavalry Brigade King's Dragoon Guards 4th Queen's Own Hussars 2nd Battalion, King's Royal Rifle Corps Mobile Divisional Signals, Royal Corps of Signals HQ, B, C, and D Troops 1st Brigade, Royal Horse Artillery A, B, and I Batterys

2nd Cavalry Brigade 2nd Dragoon Guards (Queen's Bays) 9th Queen's Royal Lancers 1st Battalion, Rifle Brigade Mobile Divisional Signals, Royal Corps of Signals E and F Troops

1st Tank Brigade 1st Light Battalion, Royal Tank Corps (until about April 1938) 2nd Battalion, Royal Tank Corps 3rd Battalion, Royal Tank Corps 5th Battalion, Royal Tank Corps

Divisional Troops 12th Lancers (administered by the 2nd Cavalry Brigade)

August 1938–April 1939

Mobile Division, , and

1st Cavalry Brigade King's Dragoon Guards 3rd Hussars 4th Queen's Own Hussars

2nd Cavalry Brigade 2nd Dragoon Guards (Queen's Bays) 9th Queen's Royal Lancers 10th Hussars

1st Tank Brigade 2nd Battalion, Royal Tank Corps 3rd Battalion, Royal Tank Corps 5th Battalion, Royal Tank Corps

Divisional troops Divisional artillery, Royal Artillery 1st Royal Horse Artillery 2nd Royal Horse Artillery Divisional engineers, Royal Engineers 1st Field Park Squadron Royal Army Service Corps 4th (until end of 1938), 10th, 11th (joined January 1939), 23rd (until end of 1938), 27th, 36th (until end of 1938), 55th (joined January 1939), and 62nd Companies Mobile Divisional Signals, Royal Corps of Signals 12th Lancers 2nd Battalion, King's Royal Rifle Corps 1st Battalion, Rifle Brigade

April-September 1939

1st Armoured Division

1st Light Armoured Brigade King's Dragoon Guards 3rd Hussars 4th Queen's Own Hussars

2nd Light Armoured Brigade 2nd Dragoon Guards (Queen's Bays) 9th Queen's Royal Lancers 10th Hussars

1st Heavy Armoured Brigade 2nd Royal Tank Regiment 3rd Royal Tank Regiment 5th Royal Tank Regiment

Divisional troops Divisional artillery, Royal Artillery 1st Royal Horse Artillery 2nd Royal Horse Artillery Divisional engineers, Royal Engineers 1st Field Park Squadron Royal Army Service Corps 10th, 11th, 27th, 55th, 62nd, and 63rd Companies Mobile Divisional Signals, Royal Corps of Signals 2nd Battalion, King's Royal Rifle Corps 1st Battalion, Rifle Brigade

September 1939–April 1940

1st Armoured Division

1st Light Armoured Brigade (until 4 November 1939) King's Dragoon Guards 3rd Hussars 4th Queen's Own Hussars

2nd Light Armoured Brigade (renamed 2nd Armoured Brigade on 14 April 1940) 2nd Dragoon Guards (Queen's Bays) 9th Queen's Royal Lancers 10th Hussars

1st Heavy Armoured Brigade (renamed 3rd Armoured Brigade on 14 April 1940) 2nd Battalion, Royal Tank Regiment 3rd Battalion, Royal Tank Regiment 5th Battalion, Royal Tank Regiment

1st Support Group 1st Royal Horse Artillery (until 20 October 1939) 2nd Royal Horse Artillery (until 20 October 1939) 60th Anti-Tank Regiment (joined 22 December 1939, left 14 February 1940) 101st Light Anti-Aircraft/Anti-tank Regiment (joined 15 February 1940) 1st Field Squadron, Royal Engineers (until 31 January 1940) 1st Field Park Troop, Royal Engineers (until 31 January 1940) 1st Battalion, Rifle Brigade (until 24 April 1940) 2nd Battalion, King's Royal Rifle Corps (until 24 April 1940)

Battle of France

From the beginning of the Second World War in September 1939, the 1st Armoured Division had been used to provide troops and material for other formations. In October, two regiments of artillery were withdrawn from the support group and dispatched to France. The following month, an armoured brigade was withdrawn to form the 2nd Armoured Division. In January 1940, engineers were removed to serve elsewhere and they were followed by an armoured regiment and the division's infantry in April and May, just prior to the division being deployed to France.

These changes left the 1st Armoured Division short of its required subordinate units, although it did contain 114 light and 143 cruiser tanks. It, however, lacked replacement tanks, spare parts, bridging and wireless equipment, and anti-tank and anti-aircraft guns. The advance elements of the division landed in France on 15 May 1940, and the first major components arrived four days later. It took another week until the entire division had been deployed. It fought in a number of engagements, most notably the Battle of Abbeville, and suffered heavy tank losses in its encounters with German forces. By 18 June, with 13 tanks remaining, it completed its evacuation to the UK.

May–June 1940 1st Armoured Division

2nd Armoured Brigade 2nd Dragoon Guards (Queen's Bays) 9th Queen's Royal Lancers 10th Royal Hussars 4th Battalion, Border Regiment (attached for fighting on 24 May)

3rd Armoured Brigade 2nd Royal Tank Regiment 3rd Royal Tank Regiment (until 22 May 1940) 5th Royal Tank Regiment

1st Support Group 101st Light Anti-Aircraft/Anti-Tank Regiment, Royal Artillery

Divisional troops 1st Armoured Divisional Signals, Royal Corps of Signals Royal Engineers 1st Field Squadron

North Africa campaign

During 1941, an armoured division was to consist of 340 tanks. Due to ongoing fighting in Egypt and Italian Libya, armoured reinforcements were requested from the UK and the 1st Armoured Division was used to provide these. With 60 M3 Stuart light tanks and 124 Crusader tanks, the division left the UK in August—just before organisational changes to the layout of UK-based armoured divisions were made. The changes, however, were not forced upon divisions serving in Africa. The division arrived in Egypt in mid-November and moved into Italian Libya the following month.