In the spring of B.C. 490 a large army and fleet were assembled in Cilicia, and the command was given to Datis, a Median, and Artaphernes, son of the satrap of Sardis of that name. Warned by the recent disaster of Mardonius in doubling the promontory of Mount Athos, they resolved to sail straight across the AEgean to Euboea, subduing on their way the Cyclades. These islands yielded a ready submission; and it was not till Datis and Artaphernes reached Euboea that they encountered any resistance. Eretria defended itself gallantly for six days, and repulsed the Persians with loss; but on the seventh the gates were opened to the besiegers by the treachery of two of its leading citizens. The city was razed to the ground, and the inhabitants were put in chains. From Eretria the Persians crossed over to Attica, and landed on the ever memorable plain of Marathon, a spot which had been pointed out to them by the despot Hippias, who accompanied the army.