The Battle of Ephesus in 498 BC was one of the turning points of the Ionian Revolt which took place between 499-493 BC. Many Greek cities including Ephesus stood up against the Persian invaders and organized the Ionian Revolt.
The Revolting Greeks marched on Sardes (Sardis) and had a victory over the Persian armies stationed in Sardis. Following this defeat Artaphernes, who was the Persian commander, called for reinforcements.
Persian armies arrived at Sardis right after the Greeks departed for Ephesus. Persians who had their army mostly made of heavy cavalry had no problem in catching up with Greek armies of rioters.
Greek armies were on the outskirts of Ephesus when Persians started to attack. Greeks or better to called Ionian Rioters were already tired of walking and fighting for several days. Persian cavalry used arrow barrages to attack and easily obliterated Greeks.
Many Greek leaders including Aristagoras who was the general of the attack on Sardis were killed. This defeat cracked the Ionian alliance against Persians and the Ionian Revolt stopped after the Battle of Ephesus in 498 BC.