During the 1920s, Harrison managed a movie theatre before moving to New York City to pursue a career as a novelist, journalist, and public relations consultant.
The same year, Harrison made headlines in The New York Times when he was arrested en route to Nicaragua, where he planned to interview the Nicaraguan dissident General Augusto César Sandino.
More successful were his non-fiction writings, including a 1931 biography of lawyer Clarence Darrow and a 1949 memoir entitled Thank God For My Heart Attack, an early installment in the genre of self-help books.
[15] Although the 1937 book is written in a lighter tone than Generals Die in Bed, it still contains "moments when satire gives way to something unfunny, and Harrison’s anti-war commitments come to the foreground.
Harrison's archive at Columbia University contains the manuscript of No Season to Weep, an unpublished 1941 novel that follows a journalist haunted by his experiences in the Spanish Civil War.