During World War II, he served in the Army Air Forces as a radioman and tail gunner, flying more than fifty bombing missions over Italy.

[3] Late in the 1950s, Miller assembled a novel from three closely related novellas he had published in The Magazine of Fantasy & Science Fiction in 1955, 1956 and 1957.

[7] In Miller's later years, he became a recluse, avoiding contact with nearly everyone, including family members; he never allowed his literary agent, Don Congdon, to meet him.

According to science fiction writer Terry Bisson, Miller struggled with depression, but had managed to nearly complete a 600-page manuscript for the sequel to Canticle before taking his own life with a firearm on January 9, 1996, shortly after his wife's death.

[2][8] The sequel, Saint Leibowitz and the Wild Horse Woman, was completed by Bisson at Miller's request and published in 1997.