In early 1916, Great Britain passed the Military Service Act, conscripting all unmarried men ages 18 to 41 into military service. Exemptions were provided for several reasons, including poor health, family hardship, and, notably, conscientious objection. A century later, English Heritage, the nonprofit that manages English historical sites, is fighting to preserve the written evidence of what happened to some of those who took the latter route during World War I, as Smithsonian reports.

The charity is spending roughly half a billion dollars to preserve graffiti scrawled on jail cells of those conscientious objectors who were imprisoned for refusing to do any kind of military service, even in non-combatant roles.

As per the Military Service Act, conscientious objectors were still required to serve in some way. Already thought of as cowards who were avoiding their civic duty at the front, they were typically required to join the Non-Combatant Corps. Those who refused to join the war effort even in a non-combatant role faced prison. One particular group of men, who came to be known as the Richmond 16, became icons of the movement for the right to say no to going to war.

They were pacifists, including Quakers and socialists, who were isolated in Richmond Castle in northern England before being shipped off to France, where they were court-martialed and sentenced to death. They weren’t actually shot, however, but were instead shipped back to England to do 10 years hard labor.

During their time in Richmond Castle, where they often subsisted on bread and water, they passed the time in part by doodling on the walls. This graffiti still remains on the castle walls, and English Heritage is restoring and protecting it, eventually opening up the cells to the public after the conservation work is done. In the meantime, you can visit the prison virtually through an interactive 3D video created by the organization.

Thanks to the precedent set by the Richmond 16, once World War II came around, a provision for so-called “absolutists” was introduced to conscription rules, allowing 3000 people to ultimately gain exemption from taking part in the war effort on the grounds of their conscience.

[h/t Smithsonian]