The Battle of Marathon (490 BC) was the culmination of King Darius I of Persia's first major attempt to conquer the remainder of the Greeks and add them to the Persian Empire, thereby securing the weakest portion of his Western border. We mostly know of this battle from Herodotus. Darius first sent Mardonius in 492 BC overland to Europe in order to strengthen Persian domination in Thrace and Macedon that had been weakened by the Ionian Revolt. Although successful in those tasks, this force fell in a storm off Mount Athos and the remains were forced to return to Asia, suffering losses along the way. In 490 BC Datis and Artaphernes were sent in a purely maritime operation to force the Cyclades islands in the central Aegean to submit to Persia and punish Eretria and Athens for the help they had sent to the Ionian revolt. Eretria was sieged and fell, and then the fleet landed in Marathon bay. There the army was met by a small force of Athenian and Plataean hoplites and defeated, despite the Persian numerical advantage. The run by a dayrunner with news of the successful outcome of the battle to Athens proved the inspiration for the sport of the marathon race that was first run in the 1896 Olympic Games.