Over 3,000,000 men volunteered to serve in the British Armed Forces during the first two years of the war. Due to heavy losses at the Western Front the government decided in 1916 to introduce conscription (compulsory enrollment).
The Military Service Act of January 1916 specified that single men between the ages of 18 and 41 were liable to be called-up for military service unless they were widowed with children or ministers of religion. Conscription started on 2nd March 1916. The act was extended to married men on 25th May 1916. The law went through several changes before the war's end with the age limit eventually being raised to 51.
It has been argued that enforced enlistment was more to do with employment circumstances, familial circumstances, physical fitness, skills and aptitudes and, to a much lesser extent religious and political grounds. This was vetted very closely by the Tribunals who had to assess a man's fitness for military service and weigh that against his usefulness to the domestic economy. As one historian has pointed out: "a farm lad, aged 19, might have escaped call-up in one part of the country whereas a 40-year old brickie from another part may have been drafted."
Conscription caused real hardships for the British people. For example, in November 1917 a widow asked Croydon Military Tribunal to let her keep her eleventh son, to look after her. The other ten were all serving in the British armed forces. A man from Barking asked for his ninth son to be exempted as his eight other sons were already in the British Army. The man's son was given three months exemption.
About 16,000 men refused to fight and these were called conscientious objectors. Most of these men were pacifists, who believed that even during wartime it was wrong to kill another human being. About 7,000 pacifists agreed to perform non-combat service. This usually involved working as stretcher-bearers in the front-line, an occupation that had a very high casualty-rate. Over 1,500 men refused all compulsory service. These men were called absolutists and were usually drafted into military units and if they refused to obey the order of an officer, they were court-martialled.
Forty-one absolutists were transferred to France. These men were considered to be on active service and could now be sentenced to death for refusing orders. Others were sentenced to Field Punishment Number One. Those found guilty before being transferred to France were sent to English prisons. Conditions were made very hard for the conscientious objectors and during the war sixty-nine of them died in prison.