At the age of 23, he received a Ph.D. in Political Science from Johns Hopkins University. From 1937 to 1946, Linebarger held a faculty appointment at Duke University, where he began producing highly regarded works on Far Eastern affairs. While retaining his professorship at Duke after the beginning of World War II, he began serving as a second lieutenant of the United States Army, where he was involved in the creation of the Office of War Information and the Operation Planning and Intelligence Board. He also helped organize the Army's first psychological warfare section. In 1943, he was sent to China to coordinate military intelligence operations. By the end of the war, he had risen to the rank of major.
In 1936, Linebarger married Margaret Snow. They had a daughter in 1942 and another in 1947. They divorced in 1949. In 1950, Linebarger married Genevieve Collins; they remained married until his death from a heart attack in 1966, in Baltimore, Maryland.
In 1947, Linebarger moved to the Johns Hopkins University's School of Advanced International Studies in Washington, DC, where he served as Professor of Asiatic Studies. He used his experiences in the war to write the book Psychological Warfare (1948), which is regarded by many in the field as a classic text. He eventually rose to the rank of colonel in the reserves. He was recalled to advise the British forces in the Malayan Emergency and the U.S. Eighth Army in the Korean War. While he was known to call himself a "visitor to small wars", he refrained from becoming involved in Vietnam, but is known to have done undocumented work for the Central Intelligence Agency. He traveled extensively and became a member of the Foreign Policy Association, and was called upon to advise then–U.S. President John F. Kennedy.
Linebarger expressed a wish to retire to Australia, which he had visited in his travels, but died at age 53 in the U.S. Colonel Linebarger is buried in Arlington National Cemetery, Section 35, Grave Number 4712. His widow, Genevieve Collins Linebarger, was interred with him on 16 November 1981.
Linebarger was long rumored to have been the original for "Kirk Allen," the fantasy-haunted subject of "The Jet-Propelled Couch," a chapter in psychologist Robert M. Lindner's best-selling 1954 collection of case histories, The Fifty-Minute Hour. According to Cordwainer Smith scholar Alan C. Elms, this fannish speculation first reached print in Brian Aldiss's 1973 history of science fiction, Billion Year Spree; Aldiss, in turn, claimed to have gotten the information from Leon Stover. More recently, both Elms and librarian Lee Weinstein have gathered much circumstantial evidence to support the case for Linebarger being "Allen," but both concede that there is no direct proof that Linebarger was ever a patient of Lindner's or that he suffered from a disorder similar to that of "Kirk Allen." Even if one accepted the likelihood that there is some connection, one would also have to conclude that the case history is so heavily fictionalized that "Kirk Allen" might be a composite of Linebarger and another patient, and that it is impossible to assign biographical details from "Allen" to Linebarger.
Linebarger's stories are unusual, even by the standards of science fiction, sometimes being written in narrative styles closer to traditional Chinese stories than to most English-language fiction. The total volume of his science fiction output is relatively small, due to his time-consuming profession and his early death: Smith's writings consist of a single novel, originally published in two volumes in edited form as The Planet Buyer (also known as The Boy Who Bought Old Earth (1964) and The Underpeople (1968), and later restored to its original form as Norstrilia (1975)), and 32 short stories (all of them gathered in The Rediscovery of Man, including two versions of the short story War No. 81-Q). All these writings suggest a rich universe developing over a long period of time, but leave much to be guessed by the reader.
Linebarger's cultural links to China are partially expressed in the pseudonym "Felix C. Forrest", which he used in addition to "Cordwainer Smith": Sun Yat-Sen suggested to Linebarger, his godson, that he adopt the Chinese name "Lin Bai-lo" (林白楽), which may be roughly translated as "Forest of Incandescent Bliss". In his later years, Linebarger proudly wore a tie with the Chinese characters for this name embroidered on it.
As an expert in psychological warfare, Linebarger was very interested in the then newly-developing fields of psychology and psychiatry, and inserted many of their concepts into his fiction. His fiction often has religious overtones or motifs, particularly evident in characters who have no control over their actions. In "Christianity in the Science Fiction of 'Cordwainer Smith'", James P. Jordan argued for the importance of Anglicanism to Linebarger's works back to 1949. However, Linebarger's daughter Rosana Hart has indicated that he did not become an Anglican until 1950 and was not strongly interested in religion until later still. In the introduction to the collection Rediscovery of Man it is indicated that from around 1960 he became more devout and expressed this in his writing. Linebarger's works are sometimes included in analyses of Christianity in fiction, along with the works of authors such as C. S. Lewis and J.R.R. Tolkien.
The bulk of Cordwainer Smith's stories are set in an era starting some 14,000 years in the future. The Instrumentality of Mankind rules Earth and goes on to control other planets later inhabited by humanity. The Instrumentality attempts to revive old cultures and languages in a process known as the Rediscovery of Man. This rediscovery can be seen either as the initial period when humankind emerges from a mundane utopia and the nonhuman underpeople gain freedom from slavery, or as a continuing process begun by the Instrumentality, encompassing the whole cycle, where mankind is constantly at risk of falling back into its bad old ways.
Smith's stories describe a long future history of Earth, from a postapocalyptic landscape with walled cities defended by agents of the Instrumentality to a state of sterile utopia in which freedom can be found only deep below the surface, in long-forgotten and buried anthropogenic strata. These features may place Smith's works within the Dying Earth subgenre of science fiction, but it can be argued that they are ultimately more optimistic and distinctive.
Smith's most celebrated short story is perhaps his first-published, "Scanners Live in Vain", which led many of its earliest readers to assume that "Cordwainer Smith" was a new pen name for one of the established giants of the genre. It was selected as one of the best science fiction short stories of the pre-Nebula Award period by the Science Fiction and Fantasy Writers of America, and appeared in The Science Fiction Hall of Fame Volume One, 1929-1964.
Linebarger's stories feature strange and vivid creations, such as: