The Samian War (440–439 BC) was an Ancient Greek military conflict between Athens and Samos. The war was initiated by Athens's intervention in a dispute between Samos and Miletus. When the Samians refused to break off their attacks on Miletus as ordered, the Athenians easily drove out the oligarchic government of Samos and installed a garrison in the city, but the oligarchs soon returned, with Persian support. A larger Athenian fleet was dispatched to suppress this agitation.