Based in Ravenscourt Park, West London, its part-time soldiers saw service at Gallipoli, in Palestine, and on the Western Front during the First World War.

This was considered a new unit, and was not allowed to retain the battle honour that detachments of the 2nd (South) Middlesex had won for service in the Second Boer War.

[11][12][13][14] When mobilisation orders arrived on 4 August 1914 about half of the 10th Battalion were with the Home Counties Division at its annual training, marching from Aldershot to Salisbury Plain.

The Home Service-only and under-age men, together with the recruits who were coming forward, remained at the depot to form the 2/10th Bn, which came into existence on 12 September under the command of Lt-Col Johnson and was almost at full strength by the end of October.

For the next four years the 1/10th Bn acted as a peacetime garrison, while suffering a steady drain of its best men to officer training and other duties.

[6] The 2/10th Battalion joined the 2nd Middlesex Brigade, which was close to full strength by 22 October 1914, and the 2nd Home Counties Division began to form in the Windsor area soon afterwards.

The battalion entrained for Devonport Dockyard on 17 July and embarked on HM Transport Huntsgreen (formerly the German Norddeutscher Lloyd shipping line's Derfflinger).

After sailing to Lemnos and then Imbros, the battalion landed on C Beach at Suvla Bay at about midnight on 8 August under the command of Lt-Col C.H.

A second attack was ordered for 16.30, but the only troops to advance were two companies of the 2/10th, who went forward about 500 yards (460 m) before discovering that they were unsupported and fell back, having lost further casualties.

[12][18][24][26][27][28][29][30] The companies were gathered during the night and the battalion was moved a few hundred yards to its left, where it dug in until relieved on 13 August.

[12][26] From Lemnos the 53rd Division was shipped to Alexandria, and began a long period of rest and recuperation guarding the Nile Valley in Egypt.

[24][33][34] The British opened the Sinai and Palestine Campaign in March 1917 when the Egyptian Expeditionary Force (EEF) advanced towards Gaza, with 53rd Division in the Desert Column.

By 13.30 the brigade had captured 'The Labyrinth', a maze of entrenched gardens, but 2/10th Middlesex's further advance was slowed up by four belts of barbed wire and at 15.30 it requested reinforcements and ammunition; two companies of 2/4th Queens (Royal West Surrey Regiment) arrived at 17.00.

2/10th Battalion moved forwards to occupy the high ground during daylight on 13 and 14 November during the Action of El Mughar, for which it received the battle honour, though not actually engaged.

A platoon of 2/10th Middlesex with two machine guns was ordered to make a feint crossing at the Auja ford while 'Shea's Group' threw troops across at other points.

While Shea's Group carried out its trans-Jordan raid, 2/10th Middlesex remained west of the river skirmishing against the Turkish cavalry screen on 29 and 30 March.

By now the EEF was suffering a manpower shortage, and on 19 August 1918 the 2/10 Bn left 160th Bde and moved back to El Qantara, Egypt, where it was broken up to provide drafts for other units.

67th (2nd HC) Division had the dual role of home defence and supplying drafts to units serving overseas.

[6][12][13][9][22][23][56] Few 3rd Line TF battalions saw service overseas, but in May 1917 the 3/10th Middlesex left 67th (HC) Division and embarked at Southampton for France.

At first it was employed in the old German front line providing digging and wiring parties for the Royal Engineers (RE) constructing new defences.

The Seaforths attacked over difficult, heavily shelled ground, behind a 'very ragged' barrage, crossed 19 Metre Hill and got about 80 yards down its forward slope.

3/10th Middlesex held its line of shell-holes, but despite holding the enemy was unable to obtain any support or ammunition.

Finally at 03.15 on 5 October some ammunition arrived, enabling the remnants of the two battalions to maintain their position through the day and following night.

10th Brigade was not engaged in the subsequent attacks made by 4th Division, though 3/10th Middlesex provided some carrying parties for the RE and Machine Gun Corps during the Battle of Broodseinde and suffering further casualties.

[6][12][13][62][63][64][65][66][b] The role of the entrenching battalions was to carry out labour duties until their personnel were required as reinforcement drafts for the infantry.

[67][68][69] When the German spring offensive opened on 21 March the battalion was working behind 15th (Scottish) Division and suffered some casualties over the next few days from the bombardment of Arras.

[67][70] Like the 3/10th Bn, the 4/10th Middlesex was formed at Ravenscourt Park in May 1915 with the role of training drafts for the battalions serving overseas.

[8] The following served with 10th Middlesex: The 10th Battalion contributed the following Battle honours to the Middlesex Regiment:[9] There are the First World War memorial plaques to the 1/10th, 2/10th and 3/10th Battalions inside St Nicholas Church, Chiswick, where the Regimental Colours of the 10th Bn (1910–21)[78] and the King's colours presented to 2/10th and 3/10th Bns after the war are displayed.

The metal plaque to the 1/10th Bn (North Wall) lists 58 members of the battalion who died on service (though it is not clear how many of these were seconded to other units).

There is also a First World War memorial plaque to the 10th Bn in the Army Reserve Centre, Deansbrook Road, Edgware.