In 1914, after compulsory call-up for British men looked increasingly likely, pacifist members of the No-Conscription Fellowship, set up in 1915, successfully campaigned to secure 'the conscience clause' in the 1916 Conscription Act: the right to claim exemption from military service.


The story of Harold Bing who was not thought to qualify for exemption....

" '18? - you're too young to have a conscience,' said the chairman. But not, apparently, too young to be sent to war. A policeman came to his home to arrest him, and he was taken to Kingston Barracks. When he refused to regard himself as a soldier, or obey military orders, he was court-martialled.
The sentence: 6 months hard labour. In the end Harold spent nearly 3 years in prison."

was not unusual but they were not actually shot for their beliefs - not all of which were, as CD points out, based on religion.