The battle of Lade (494 BC) was the decisive battle of the Ionian Revolt, and was a crushing Persian naval victory that eliminated Ionian naval power and left the individual Ionian cities exposed to attack.
At the time of the battle Miletus sat on the southern side of a very large bay at the mount of the Maeander River. Lade was an island just off the coast to the west of the city. Since then the bay has filled in, and both Lade and Miletus are inland with the river running some way to their north.
The first Persian counterattack, in 497-496, involved three separate armies, which successfully recaptured parts of the Hellespont and Propontis regions, but it came to an end after the Carians ambushed and destroyed one of the three armies at Pedasa in 497 or 496. This was followed by a pause in recorded Persian activities, before in 494 they decided to focus all of their efforts against Miletus, where the revolt had broken out.
The Ionian leaders met at the Panionium, a sacred sanctuary on the northern side of Mt Mycale, on the opposite side of the Maeander estuary. They decided to focus all of their efforts on producing as large a navy as possible, leaving the defence of the city of Miletus to the Milesians. If the Persian fleet could be defeated, then the city would be safe.
The Ionians managed to raise 353 ships. The size of the individual contingents reflected the relative power of the individual cities, and also demonstrated how much more powerful they were than the main cities of mainland Greece at this time. The Milesians formed the eastern wing of the fleet, and provided 80 ships. Next in line were the Prieneans, who provided 12. Myous provided 3, Teos provided 18, Chios provided 100. The Erythraeans provided 8 and the Phocaeans 3 (the city had lost a great deal of its population to emigrate at the time of the original Persian conquest). The only non-Ionian contribution came from Lesbos in Aeolia, which provided 70 ships. Finally the Samians formed the western end of the fleet, with 60 ships.
Although this was an impressive fleet, the Ionians were outnumbered by the Persian fleet, which was around 600 strong. The largest, and best manned, part of the Persian fleet came from Phoenicia. The Persians were accompanied by the tyrants who had been expelled from the Ionian cities at the start of the revolt.
After the Persians arrived at Miletus a standoff developed. During this period the morale of the Ionian fleet began to suffer. Herodotus records two reasons for this. The first was the fault of Dionysius, commander of the small Phocaean contingent. He was given command of the fleet, probably because he wasn't from any of the larger states. For a week he put the fleet into intense training, but the argumentative Ionians then virtually mutinied and refused to continue with the training.
The second factor was a deliberate Persian campaign to undermine morale and attempt to break up the Ionian fleet. They got the tyrants to send messages to the contingents from their home cities threatening them with enslavement and destruction if they fought on, but offering to respect their property and lives if they abandoned the fight. At first all of the contingents refused to listen to this message, but eventually the Samians were won over. According to Herodotus their decision was partly due to a belief that the war couldn't be won, and partly due to the general collapse of discipline in the Ionian camp.
After an unknown period of standoff, the Persian fleet put to sea and prepared to attack the Ionians. The Ionian fleet formed up into a column, and the battle began. At this point Herodotus admits that he can't say who fought well and who fought badly in the battle, as each Ionian city blamed the others for the defeat.
The battle was lost by the treachery of the Samians, who hoisted their sails and left the fleet. Only eleven of their sixty ships refused to abandon the cause, and stayed to fight on. Later the names of the crews of these eleven ships were inscribed on a column in the town square, but in the short term the deserters were rewarded for their actions, and Samos was left alone during the persecutions that followed the Persian victory.
After the Samians sailed away they were followed by the Lesbian contingent. This meant that a third of the fleet had deserted the cause. Most of the remaining crews realised that the battle was lost, and also fled from the scene.
Part of the Ionian fleet refused to flee, most notably the large Chian contingent. This part of the Ionian fleet fought on, inflicting heavy losses on the Persians, but eventually most of the Chian ships had been lost. The survivors fled north across the bay and beached on the southern shores of Mt Mycale. They attempted to escape north across the peninsula, but were massacred when they entered Ephesian territory. This may have been because of a long standing rivalry between the two cities, or, as Herodotus suggests, because the locals mistook the approaching Chians for bandits.
The Persian victory at Lade effectively smashed the Ionian Revolt. Miletus was besieged and sacked, and never really recovered from the disaster. The individual Ionian cities were now exposed to attack. During the rest of 494 and the start of 493 the Persians carried out a devastating campaign across Ionian and the Hellespont regions, but they then switched to a policy of reconciliation. In 492 they even went as far as deposing the tyrants they had restored after the battle of Lade, and replacing them with democratic regimes.