This comes from The Company Man from Herman Melville:
"Have you no charity, friend?" here in self-subdued tones, singularly contrasted with his unsubdued person, said a Methodist minister, advancing; a tall, muscular, martial-looking man, a Tennessean by birth, who in the Mexican war had been volunteer chaplain to a volunteer rifle-regiment.
I am wondering what the phrase "has been X to a Y" mean. Does it mean "was all manner of things from X to Y" or simply "had been X and then later Y"? I never heard the phrase "had been X to a Y" before.