what does "B.T.O"here mean?
Ferris pulled out his address book to verify a number. He turned the pages with growing attentiveness. Names and addresses from New York, the capitals of Europe, a few faint ones from his home state in the South. Faded, printed names, sprawled drunken ones. Betty Wills: a random love, married now. Charlie Williams: wounded in the Hürtgen Forest, unheard of since. Grand old Williams—did he live or die? Don Walker: a B.T.O. in television, getting rich. Henry Green: hit the skids after the war, in a sanitarium now, they say. Cozie Hall: he had heard that she was dead. Heedless, laughing Cozie—it was strange to think that she too, silly girl, could die. As Ferris closed the address book, he suffered a sense of hazard, transience, almost of fear.