Aristagoras felt that some further strength was needed, and determined to seek it in European Greece.

Repulsed from Sparta, which was disinclined to so distant an expedition, he applied for aid to cities on which he had a special claim.

Miletus counted Athens as her mother state; and Eretria was indebted to her for assistance in her great war with Chalcis.

Applying in these quarters Aristagoras succeeded better, but still obtained no very important help.
Athens voted him twenty ships, Eretria five and with the promise of these succors he hastened back to Asia.
The European contingent soon afterwards arrived; and Aristagoras, anxious to gain some signal success which should attract men to his cause, determined on a most daring enterprise.

This was no less than an attack on Sardis, the chief seat of the Persian power in these parts, and by far the most important city of Asia Minor.