In 1966, the work of another writer (Hemingway scholar Philip Young) prompted Morrell to move to the United States, where he studied with Young at Penn State and received his M.A. and Ph.D. in American literature. There, he also met the distinguished fiction writer William Tenn (real name Philip Klass), who taught Morrell the basics of fiction writing. The result was First Blood, a novel about a returned Vietnam veteran suffering from post-trauma stress disorder who comes into conflict with a small-town police chief and fights his own version of the Vietnam War.
That "father" of all modern action novels was published in 1972 while Morrell was a professor in the English department at the University of Iowa. He taught there from 1970 to 1986, simultaneously writing other novels, many of them national bestsellers, such as The Brotherhood of the Rose (the basis for a highly rated NBC miniseries starring Robert Mitchum). Eventually wearying of two professions, he gave up his tenure in order to write full time.