The 31st Division was an infantry division of the British Army. It was raised in the Great War by volunteers from Kitchener's Army and formed in April 1915 as part of the K4 Army Group and taken over by the War Office on 10 August 1915. Comprising mainly infantry battalions from Yorkshire and Lancashire, the division was sent to Egypt in December 1915 before moving to France in March 1916 and spent the remainder of the First World War in action on the Western Front. The 31st Division was the quintessential New Army division, being made up entirely of Pals battalions.

The 31st Division's first major action was on the first day on the Somme (1 July 1916). The division suffered 3,600 casualties and failed to reach any of its objectives. Later it served at the Battle of the Ancre and at Oppy Wood. It took part in the defence against the German spring offensive in early 1918, and finally in the victorious battles of the Hundred Days Offensive.

On 6 August 1914, less than 48 hours after Britain's declaration of war, Parliament sanctioned an increase of 500,000 men for the Regular Army, and on 11 August the newly-appointed Secretary of State for War, Field Marshal Earl Kitchener of Khartoum, issued his famous call to arms: 'Your King and Country Need You', urging the first 100,000 volunteers to come forward. This group of six divisions with supporting arms became known as Kitchener's First New Army, or 'K1'. The flood of volunteers overwhelmed the ability of the army to absorb and organise them, and by the time the Fifth New Army (K5) was authorised, many of its constituent units were being organised as 'Pals battalions' under the auspices of mayors and corporations of towns up and down the country.

In late May and early June 1915 the units of the 31st Division began to assemble at South Camp, Ripon, where brigade training began in earnest. Musketry training was finally begun in August, and in September the division moved to Hurdcott Camp at Fovant where the division received SMLE service rifles and carried out final intensive battle training in the Salisbury Plain Training Area.

On 29 November 1915 the division received warning orders to join the British Expeditionary Force in France, and advance parties set out for the embarkation ports of Folkestone and Southampton. At the last minute, the destination was changed to Egypt, the advance parties were recalled, and on 7 December the troops embarked at Devonport.

The division reached Port Said between 24 December and 23 January 1916 and went into the Suez Canal defences at Qantara. On 26 February orders arrived to reverse the process and on 1 March the division began re-embarking at Port Said. It unloaded at Marseille between 6 and 16 March and then concentrated in the Somme area as part of the BEF. It remained on the Western Front for the rest of the war.

The division was introduced to trench warfare in March in front of Beaumont-Hamel and Y Ravine. Although this was a quiet sector of the line, the troops suffered their first casualties during this short tour, mainly from German Minenwerfers (trench mortars). Shortly afterwards the 31st Division formed its own light trench mortar batteries (TMBs). It also provided working parties to assist the 252nd Tunnelling Company, Royal Engineers, digging the Hawthorn Ridge mine that was to be exploded to launch the forthcoming Battle of the Somme. Over the following weeks the battalions took their turns in the routine of trench holding, working parties, patrolling and trench raiding, with a constant drain on manpower from shelling and snipers.

The 92nd Brigade held the front line trenches during the British bombardment in the days leading up to the battle, suffering significant casualties from the German counter-bombardment. The night before the battle, working parties from the 92nd Brigade were out in No man's land cutting lanes through the British barbed wire for the assaulting troops to pass through. It then withdrew into the support trenches, to hold the front line while the other two brigades attacked on 1 July. Despite all the preparation and high hopes, the First day on the Somme was a disaster for 31st Division. 93 and 94 Brigades went 'over the top' at 07.30 on 1 July, 10 minutes after the explosion of the nearby Hawthorn Ridge mine had alerted the enemy. Their objective was the village of Serre. The advancing lines were almost annihilated by German machine guns and shellfire, and only a few parties got into the enemy front line, where they remained pinned down. The division was unable to get any support to them across the fire-swept No man's land for the rest of the day.