 Meanwhile, Machiavelli's enforced retirement led him to other literary activities. He wrote verse, plays, and short prose, penned a study of The Art of War (published in 1521), and produced biographical and historical sketches. Most importantly, he composed his other major contribution to political thought, the Discourses on the Ten Books of Titus Livy, an exposition of the principles of republican rule masquerading as a commentary on the work of the famous historian of the Roman Republic. Unlike The Prince, the Discourses was authored over a long period of time (commencing perhaps in 1514 or 1515 and completed in 1518 or 1519, although again only published posthumously in 1531). The book may have been shaped by informal discussions attended by Machiavelli among some of the leading Florentine intellectual and political figures under the sponsorship of Cosimo Rucellai.