The Athenians had been preparing for war with the Persians since the mid-480s BC, and in 482 BC the decision was taken, under the guidance of the politician Themistocles, to build a massive fleet of triremes that would be necessary for the Greeks to fight the Persians.[93] The Athenians did not have the man-power to fight on land and sea; therefore combatting the Persians would require an alliance of several Greek city states. In 481 BC Xerxes sent ambassadors around Greece asking for earth and water, but making the very deliberate omission of Athens and Sparta.[94] Support thus began to coalesce around these two states.