A clash between civilizations
The huge disparity of means was known to all. Shortly before moving with his army towards Greece, Herodotus tells that(his stories were written some decades after the events narrated) the king Xerxes could not understand why the Greeks thought to resist her invasion and preferred not to submit: "How could a few free men oppose such a great army? If they were subject to only one command, as is customary among us, for fear of this master perhaps they might fought valiantly, and forced by sjambok, they might have even attacked more of their opponents; the Greeks who are intolerant of any order will not certainly "...
At this point, a Greek exile intervened in the Court of the King of Persia, and the question posed by the King was been replied as followed: "O King, be aware that the Greeks, despite being free, they aren't completely in that condition, because on each of them is a terrible master: the law, which they fear even more than your subjects have not for you".
Herodotus clearly made it present that was not only a clash between two States, but that in the game were there were two opposing political beliefs: on one hand, the Eastern monarchy with its hierarchical structure and manifest, from the other hand, the city founded on the free association of persons. Of course, behind the words of Herodotus we can feel the echo of a propaganda, but they effectively express the decisiveness that animated the resistance of the Greeks.
In addition, the Organization for both civil and military purposes of the Greeks was to rise to the occasion, as well as the awareness was to fight for a just cause. A defeat would have meant, for the Greeks, the subjection to the Persian Empire, and would have made it impossible for the survival of a democratic regime such as that of Athens: in other words, this great "invention" policy, in which lies a fundamental historical heritage transmitted by the Greeks to modern culture, would have been stifled in the bud.