The poem—which most speculate proceeded in chronological order—was likely divided into triads with a "concentric, symmetrical structure". In the first seven books, Ennius wrote about mythical and historical past episodes, whereas in the following eight (and eventually, eleven), he wrote about contemporary events. Although most of the poem has been lost, there is a "traditional"—albeit conjectured—organization for the book. Books 1–3 cover the end of the Trojan War in 1184 BC, to the reign of the last king of Rome, Lucius Tarquinius Superbus 535–509 BC. Books 4–6 revolve around the early Roman Republic up until the Pyrrhic War in 281–271 BC. Books 7–9 deal briefly with the First Punic War (264–241 BC) before covering the Second (218–201 BC) in more detail. Books 10–12 focus on the Second Macedonian War. (The ending to these three books is unclear; Ennius might have concluded with an epilogue, or detailed Rome’s campaign against Antiochus III the Great, 192 BC.) Books 13–15 detail the Roman–Seleucid War (192–188 BC) until the events of the Aetolian War (191–189 BC). According to Werner Suerbaum and Werner Eck, it is likely that Ennius chose to end the original portion of his opus with the Aetolian War because of the role played in the conflict by one of his patrons, Marcus Fulvius Nobilior.