Pressure for the introduction of conscription in Britain - the only Great Power without universal military service - had grown in the early years of the 20th century. The National Service League, founded in 1906 after the Boer War, had more than 315,000 members and 'supporters' at its peak in 1912. Five consecutive conscription bills were tabled in Parliament in the years before 1914.

Yet opposition to universal military service remained strong. The governing Liberal Party opposed the idea, as did large sections of the Labour Party and some Conservatives. Even after war broke out in August 1914, the Cabinet unanimously dismissed Winston Churchill's proposal for 'compulsory [military] service'. British strategy, as the foreign secretary Sir Edward Grey argued, was 'to pursue a European policy without keeping up a great army'.

However, the high casualty rates on the Western Front and the falling number of voluntary recruits for the 'New Army' quickly pushed the issue of conscription to the top of the political agenda. After the formation of a coalition government under Asquith in May 1915, the Conservative Party and the Liberal minister of munitions David Lloyd George orchestrated a powerful media campaign in favour of universal military service.

In January and May 1916, two Military Service Acts were passed by Parliament, ensuring that all those eligible to serve 'king and country' were now forced to report for duty. Various categories were exempt - among others, those whose work was essential to the war effort, those deemed medically unfit for service and those who could show a 'conscientious objection' to active participation in the war.

There were many shades of opinion on the British left about a general anti-war campaign, but it proved far easier to mobilise around the single issue of conscription. From 1915 onwards, conscription was presented by groups such as the Independent Labour Party (ILP) as a fatal infringement of civil liberties that would allow 'Prussian militarism' to enter Britain by the back door. Despite police harassment and the restrictions of the Defence of the Realm Act, the ILP and other organisations such as the No-Conscription Fellowship distributed leaflets and held meetings that roundly condemned the idea of a British conscript army.

With the passing of the Military Service Acts in 1916, the attention of many anti-conscription activists turned increasingly from stopping conscription per se to helping its most obvious victim: the conscientious objector. Approximately 16,000 men were recorded as 'COs' during the First World War.

They fell into various categories. Some opposed the 'imperialist' war on political grounds; others - including many Quakers - opposed it for religious reasons. Some COs felt able to support the war effort as non-combatants. 'Absolutists', however, opposed undertaking any work whatsoever that aided Britain's prosecution of the war.

The fate of British COs was usually decided by local tribunals, set up under the terms of the Military Service Act to judge whether individuals should be granted exemption from military service. Many who appeared before them offered practical arguments for exemption (such as physical or medical disability, employment on work of 'national importance', or family or business situations that could not survive their absence), rather than principled opposition to the war.

Those who applied for exemption on grounds of conscience were often given short shrift. The No-Conscription Fellowship worked tirelessly on such cases, giving advice about how to present applications to the tribunal and publicising the fate of COs who were imprisoned as 'deserters' after losing their appeals.

Such men, however, constituted a tiny minority of the British army. Although the anti-conscription movement in Britain had no parallels elsewhere in Europe, it was still a relatively minor thorn in the government's side. Public opinion generally had little sympathy for COs treated harshly in prison. Organisations such as the ILP and the No-Conscription Fellowship were stigmatised in the jingoistic sections of the press as 'cowards', 'peace cranks' and 'pasty faces'.

Events in Cardiff in November 1916, when a 'peace conference' was violently interrupted by a mob of 'patriots', vividly illustrated the depth of public hostility towards those who were seen to be hindering the successful prosecution of the war.