When the winter was now ending the Boeotians took Oropus, where the Athenians had a garrison, by treachery. And they had the cooperation of some men of Eretria and of Oropus itself who were plotting for the revolt of Euboea. For since the place is opposite Eretria, it was impossible, while the Athenians held it, that it should not injure greatly both Eretria and Euboea in general.
Now, therefore, that they had Oropus in their possession, the Eretrians came to Rhodes and invited the Peloponnesians to Euboea. They, however, were more intent upon relieving Chios, which was in distress; so they put off from Rhodes and sailed with all their ships.
When they had arrived in the neighbourhood of Triopium they saw the Athenian fleet on the high seas as they were sailing from Chalce;