He greatly under-estimated the difficulties of the conquest of European Greece; but that he regarded it as a serious undertaking is shown by the magnitude of the expedition which was despatched to Europe under Mardonios.
The strategic plan of that campaign was similar to that adopted in the expedition of 480. The disaster off Athos modified his design. It showed him the dangers attendant upon the voyage of a large fleet by that circuitous route in those stormy seas,—a voyage which would be protracted by the necessity of keeping touch with the slow advance of the army on land.
He determined, therefore, that the plan of the co-operation between army and fleet must be renounced, and that the attack must be made by the short sea-route through the islands of the Ægean.
This change of design brought a further modification in its train.
The transport of the huge numbers of a Persian levy of the first magnitude was out of the question in the vessels of those times; and so the new expedition was expressly limited in its apparent scope to the punishment of those states which had taken part with the Ionians.
In accordance with the methods of Persian policy under such circumstances, it was sought to minimize the danger of the expedition by detaching as many of the states as possible from the defence before the attack was actually made. So in the year 491 Persian heralds were despatched to the various cities of Greece with orders to demand earth and water from them. Messengers were also sent to the tributary states on the Asiatic coast, ordering them to prepare warships and transports. Herodotus says that many of the states of the European mainland, and all the islands to which application was made, obeyed the demand; but it is noticeable that he does not mention any by name, save only the island of Ægina.
The action of Ægina provoked alarm at Athens, and this, coupled with the desire to get an old enemy into trouble, caused Athens to make representations at Sparta with regard to the conduct of the Æginetans.[56]
To follow the confused details given by Herodotus of the relations between Athens and Ægina is no part of the purpose of this work, except in so far as they affect the larger question of the relations with Persia. In the present instance Kleomenes, of the senior branch of the Royal house of Sparta, did interfere in Ægina in consequence of the Athenian representations. His first visit to the Island was ineffective. The Æginetans objected that he was acting solely on his own authority, and not on that of the Spartan Government; otherwise, so they said, the other king would have accompanied him. This objection was suggested to them in a letter of Demaratos, his colleague in the kingship.[57]
ALLEGED MEDISM OF ÆGINA.
The action of Demaratos rendered the relations between the two kings so hostile, that Kleomenes intrigued to bring about the deposition of his colleague and rival. In this he was successful, and Leutychides succeeded to the kingship which Demaratos had held.