At the start of 1914 the British Army had a reported strength of 710,000 men including reserves, of which around 80,000 were regular troops ready for war. By the end of World War I almost 1 in 4 of the total male population of the United Kingdom of Great Britain and Ireland had joined, over five million men.
One early peculiarity was the formation of "Pals battalions": groups of men from the same factory, football team, bank, and similar, joining and fighting together. The idea was first suggested at a public meeting by Lord Derby; within three days, he oversaw volunteers sufficient for three battalions. Lord Kitchener, the Secretary of State for War, gave official approval for the measure almost instantly and the response was impressive. Manchester raised fifteen specific 'Pals' battalions; one of the smallest was Accrington, in Lancashire, which raised one. The drawback of 'Pals' battalions was that a whole town could lose its military-aged menfolk in a single day.
The government demand for men continued unabated, and after the first call in August for 500,000 men a further 3.5 million were called-for before the year's end. The pre-war calculations had supposed that the British Expeditionary Force would lose around 40% of its manpower in the first six months of fighting, Kitchener's predictions of three years fighting and a million men needed being regarded as incredible. The seven divisions of the BEF, totalling 85,000 men, had been landed in France at the outbreak of war; casualties in the first three months totalled almost 90,000. By mid-1915, this total had risen to around 375,000 men even before the autumn offensives and the rate of recruitment was falling off, for a number of reasons.
In 1914 the total available number of men of military age was 5.5 million, with around 500,000 more reaching the age each year. By late September, 2.25 million men had been enlisted and 1.5 million were in reserved occupations. Of the rest, the recruiters had uncovered a dismaying fact — almost two in every five volunteers were entirely unsuitable for military service on the grounds of health. When volunteer numbers fell to around 70,000 a month after the Dardanelles Expedition, the government felt forced to intervene, although they initially avoided conscription. A National Registration Act in 1915 created a register that revealed the number of men still available and they were targeted in a number of ways. The skills of advertising were brought to bear with posters, public meetings, tales of German atrocities, and the threat of shame. The 'Derby Scheme' used door-to-door visits to gather men to 'attest' to serve if needed.
Many public institutions of all sorts mobilized to help recruit for the war. The women's suffrage movement was sharply divided, the slight majority becoming very enthusiastic patriots and asking their members to give white feathers (the sign of the coward) in the streets to men of military age who had not joined the army.
The popular music hall artistes of the time worked enthusiastically for recruitment. Harry Lauder toured the music halls, recruiting young soldiers on stage in front of the audience, often offering 'ten pounds for the first recruit tonight'. Marie Lloyd sang a recruiting song I didn't like you much before you joined the army, John, but I do like you, cockie, now you've got yer khaki on (1914). Vesta Tilley sang The Army of Today's alright.
Conscientious objection was included in the 1916 Acts, with objectors appearing before local tribunals to obtain exemption. Around 7000 men were granted non-combatant duties, while a further 3000 ended up in special work camps. 6000 were imprisoned. Some forty two were sent to France to potentially face the threat of a firing squad. This threat was more real to thirty five who were formally sentenced to death, but immediately reprieved, with ten years penal servitude substituted.