The Quakers did it out of principle though. They requested non-combat duties, like ambulance or other support positions. They got locked up for it. They then confronted racism in the prison systems, so they got kicked out of prisons & sent to work (forced labour) at places like Insane Asylums... which they then exposed as being hell-holes of disease, corruption & death.
After the war was they helped all the Japanese-Americans who'd been sent to concentration camps. Quakers were legit back in the day!