The 84th was one of the few Regiments of Foot lacking a county designation and the title was given in recognition of the fact that the unit had been raised in York in 1793, with a second battalion in Preston, Lancashire in 1808.

[11][12] In total, 22 battalions of the regiment served during the Great War, losing 8,814 officers and men killed in action.

[14] During the Battle of the Somme, eight battalions of the Yorks and Lancs' went over the top on the first day, 1 July 1916, suffering huge casualties.

[14] While the battalion was still in France Private Samuel Harvey was awarded the York and Lancs' first Victoria Cross since the regiment's creation in 1881.

Following the armistice of 11 November 1918 troops from the York's and Lancaster Regiment were involved in a mutinous riot at the Clipstone Camp, Nottinghamshire, following disquiet at the slow rate of being demobilised.

The battalion, after evacuation to the United Kingdom in May 1940, was sent to Scotland where the 15th Brigade was reunited with rest of the division, later being posted to Northern Ireland in March 1942.

The battalion, as in the aftermath of Monte Cassino, remained at Anzio until late May, where it took part in Operation Diadem, and in June was withdrawn from the front line, returning to the Middle East in July, where the battalion remained for the next seven months, resting and refitting after nearly a year of continuous action in Sicily and Italy.

[20] Most of their casualties in this battle were suffered in the withdrawal by the Royal Navy which came under heavy air attack from the German Luftwaffe.

On returning to Egypt, they became part of the 70th Infantry Division used in the breakout from Tobruk, where they suffered heavy casualties as one of the lead battalions.

In 1942, they were transferred, along with the rest of the 70th Infantry Division, to India and Burma where they took part in the Second Chindit Campaign and the Arakan offensive toward the end of the war.

The Hallamshires were sent to Iceland and the United Kingdom in April 1942, not seeing active service until the battalion was landed in Normandy soon after D-Day in June 1944 and fought its way through France, Belgium (where Corporal John Harper was awarded the regiment's fifth Victoria Cross), and into the Netherlands, where it was part of the bitter fighting that led to the eventual capture of Arnhem in April 1945.

From October 1944 to January 1945, the regiment served as infantry due to the shortage of manpower in the British Army at the time.

Taking part in the Dunkirk evacuation, the battalion returned to England in June 1940 and remained there on anti-invasion duties for the next two-and-a-half years.

After spending three months resting, refitting and training, the battalion then, in early September 1943, took part in the Allied invasion of Italy, suffering very heavy casualties.

[24] Meanwhile, the 7th Battalion, which was raised in 1940, was in India (from December 1942), but served mainly on the North-West Frontier, before being moved to Burma in 1945, too late to contribute to the defeat of the Japanese.

The 150th Regiment used Lee tanks with which it fought at the Battles of Imphal, Kohima and Meiktila and on the advance to Rangoon (Operation Dracula).