The main focus of the book are events in mainland Greece, principally the Second Persian invasion of Greece under Xerxes (1-19, 27-39), Themistocles' construction of the Peiraeus and Long walls and his defection to Persia (41-50, 54-59) and the Pentecontaetia (60-65, 78–84, 88). Interweaved with this is an account of events in Sicily, focussing on Gelon of Syracuse's war with the Carthaginians (20-26), his successors' prosperity and fall (51, 53, 67-68), and the Syracusans' war with Ducetius (76, 78, 88-92).