John M. Collins began to amass military experience when he enlisted in the Army as a private in 1942. Thirty years and three wars later, in 1972, he retired as a colonel. He spent the next quarter century as the leading analyst on military and defense issues at the Congressional Research Service. He has written a dozen books and often contributes to Proceedings . Six years ago he established the Warlord Loop. The handpicked military and civilian members of the Loop, who represent every point on the public opinion spectrum, have debated crucial national security issues online ever since. Colonel Collins recently conducted a survey in which he asked members to identify two books, fiction or nonfiction, that helped shape their professional perspectives. A cross-section of responses follows. The book most named? Anton Myrer's Once An Eagle . The runner-up? Viscount Slim's Defeat into Victory .