Conscience, as Tobias Kelly points out in this intriguing, original book, is a curious thing. During the Second World War, the British government formally recognised the legitimacy of conscientious objection to military service, but never got round to defining exactly what it thought that meant. But then conscientious objectors (COs) themselves were not much clearer about it either. To some of them, conscience was above all about freedom of choice, the untrammelled right of the individual to make his or her own decisions. To others, conscience was not a liberty but an obligation: a matter not of picking or choosing which particular moral high ground to take a stand on but of recognising that one was guided to take such a position by an unseen, unknowable force and that one had a duty to defend it regardless of the personal cost. Kelly’s book follows the stories of a few of the roughly sixty thousand Britons who declared between 1939 and 1945 that they could not in good conscience kill or assist in killing.

Britain had been through this before in the First World War. The Military Service Act of January 1916, which introduced conscription, included a right to exemption based on sincere personal opposition to violence. This was natural enough in a country with an enduring Nonconformist tradition, although the British government, unlike the American one, did not insist that conscientious objection be inspired by religious belief. About sixteen thousand men were registered as COs before the armistice, two in three of them being ultimately granted some kind of conditional exemption from fighting which substituted non-combatant war work for regular army service. Roughly six thousand were refused any exemption at all, however, and in a clumsy attempt at coercion several dozen of them were sent to France and sentenced to death by firing squad for refusing to obey orders. A Parliamentary uproar provoked the War Office to hastily commute the sentences to penal servitude. The lesson the government learned from this experience was that attempting to terrorise conscientious objectors into uniform was futile. This would guide its policy in the war to come.

During the 1930s, the pacifist movement became a significant force in British politics. The Oxford Union famously voted in 1933 that in no circumstances would it fight for king and country, while Canon Dick Sheppard’s Peace Pledge Union (PPU) persuaded over 130,000 people to renounce war and refuse