<P> Other sources include Justin's (2nd century AD) epitome of Pompeius Trogus' Historiae Philipicae and a summary of Arrian's Events after Alexander, by Photios I of Constantinople . Lesser supplementary sources include Curtius Rufus, Pausanias, Pliny, and the Byzantine encyclopedia the Suda . In the field of philosophy, Diogenes Laertius' Lives and Opinions of Eminent Philosophers is the main source; works such as Cicero's De Natura Deorum also provide some further detail of philosophical schools in the Hellenistic period . </P> <P> Ancient Greece had traditionally been a fractious collection of fiercely independent city - states . After the Peloponnesian War (431--404 BC), Greece had fallen under a Spartan hegemony, in which Sparta was pre-eminent but not all - powerful . Spartan hegemony was succeeded by a Theban one after the Battle of Leuctra (371 BC), but after the Battle of Mantinea (362 BC), all of Greece was so weakened that no one state could claim pre-eminence . It was against this backdrop that the ascendancy of Macedon began, under king Philip II . Macedon was located at the periphery of the Greek world, and although its royal family claimed Greek descent, the Macedonians themselves were looked down upon as semi-barbaric by the rest of the Greeks . However, Macedon had a relatively strong and centralised government, and compared to most Greek states, directly controlled a large area . </P> <P> Philip II was a strong and expansionist king and he took every opportunity to expand Macedonian territory . In 352 BC he annexed Thessaly and Magnesia . In 338 BC, Philip defeated a combined Theban and Athenian army at the Battle of Chaeronea after a decade of desultory conflict . In the aftermath, Philip formed the League of Corinth, effectively bringing the majority of Greece under his direct sway . He was elected Hegemon of the league, and a campaign against the Achaemenid Empire of Persia was planned . However, while this campaign was in its early stages, he was assassinated . </P> <P> Succeeding his father, Alexander took over the Persian war himself . During a decade of campaigning, Alexander conquered the whole Persian Empire, overthrowing the Persian king Darius III . The conquered lands included Asia Minor, Assyria, the Levant, Egypt, Mesopotamia, Media, Persia, and parts of modern - day Afghanistan, Pakistan, and the steppes of central Asia . The years of constant campaigning had taken their toll however, and Alexander died in 323 BC . </P>

During the hellenistic period there were important achievements in which