The battle of Pedasus or Pedasa (497 or 496 BC) was the third in a series of battles between the Persians and Carian rebels during the Ionian Revolt, and was a major Persian defeat that effectively ended their first large scale counterattack against the rebels.
The Ionian Revolt broke out in 499, but it didn't spread to Caria until 498, in the aftermath of the Ionian raid on Sardis (498). In 497 the Persians launched their first major counterattack against the rebels, commanded by three son-in-laws of Darius I. One of those generals, Daurises, led his army to the Hellespont, where he captured Dardanus, Abydus, Percote, Lampsacus and Paesus.
He was forced to abandon this successful campaign when news reached him of the Carian revolt. He turned south and headed towards the Carian border. This news soon reached the rebels, who decided to make a stand on the River Maeander. The resulting battle of the Maeander (497 BC) was a major Persian victory. The Carian survivors retreated south to the sanctuary of Zeus the God of War at Labraunda, where they were debating whether they should surrender or flee from Anatolia when they received reinforcements from Miletus. This restored their morale, and they decided to stand and fight. The Persians attacked, and inflicted a second heavy defeat on them, possibly at Labraunda (497 BC).
After this second victory, there appears to have been a pause in the campaigning. Both battles were described as hard fought, so the Persians may have needed time to regroup. The Carians had suffered two heavy defeats, and were in even more need of a rest. Unfortunately we don't know how long the pause was. All we know from Herodotus is that the next battle took place 'Some time after this disaster', when both sides had had time to regroup. This probably places the battle of Pedasa early in 496, the next campaigning season, but it may have been fought later in 497.
The campaign was renewed when the Persians decided to attack the Carian cities. The Carians, commanded by Heraclides, son of Ibanollis, from Mylasa, set up an ambush at Pedasa (or Pedasus), in the south-west of Caria (just to the south of Mylasa).
The Persians fell into the trap during a night march, and their army was almost wiped out. Amongst the dead were Daurises himself, along with Amorges, Sisimaces and Myrsus son of Gyges.
This disaster effectively ended the first Persian counterattack. The Persians had already lost Hymaees, the second of their three commanders, who died of illness while campaigning around Ilium. With two commanders and one of their armies lost, they were forced to pause, and didn't return to the offensive until 494.