Map of the Achaemenid Empire

Throughout his reign, Darius I the Great had to contend with repeated revolts in his vast Empire. One of the best-known episodes in Western culture is the Ionian revolt, followed by the offensive in Thrace and mainland Greece, halted by the battle of Marathon (first of the Median Wars). Despite this, the Achaemenid Persian Empire was the largest in antiquity (6 million km2); according to a foundation plaque in Persepolis, Darius ruled «from the Sakas beyond Sogdiana, to Kush (Nubia), from the Indus to Sardis», the first example of a «World Empire» in history, bringing together so many regions in a single unitary state.