Petrarch wrote his nine book epic poem in hexameters, the standard metre for Epic in Classical Latin and consisting of six metrical feet. Petrarch probably intended his incomplete poem to be twelve books total based on Virgil's "Aeneid," (also in hexameters). The main story centers around the time period of the Spanish campaign (205 BC) to the end of the Battle of Zama (202 BC). This is based on Livy's third decade of his "History of Rome."