The reasons for the Greek victory against the Persians in 490 to 480/479 BC was a mixture of exceptional leadership, skilful tactics and strategy, superior weapons and soldiers, and Greek unity. Strong leadership was the most important aspect of the Greek defence, as without the intelligence and bravery of the leaders, the Greeks would have been easily defeated. As a result of the excellent leadership; Greek tactics, strategy, and unity were greatly strengthened. Combined with their better weapons and soldiers, the Greeks held the advantage and seized opportunities at the perfect moment. Also, with each victory the Greeks grew more confident of success and defiant of the Persian attempts to invade. The poor organisation and disarray of their enemy led to an undermining of the Persian might and further improved Greece's chances of success.
Despite the lack of official unity throughout Greece, many brilliant leaders from individual cities combined their skills and abilities to defeat the Persians. Greek leadership developed from weak and conflicting to united and strong, directly contributing to a Greek victory over the Persians as they promoted unity, strategy and a determination to defend their homeland. Without this firm leadership, the other reasons for Greek success would not exist as strongly.
Despite the Greeks strong defiance of Persia, Darius and many of his council still foolishly believed that they could easily overcome the Greeks. They were short sighted as they saw only personal fame and glory to be gained, and as a result, did not prepare for the possibility of difficulties, and certainly not defeat. This arrogance reflects the poor leadership from the Persian side, which aided the Greeks in defeating them.
When Darius invaded, there was conflicting debate at Athens as to whether they should defend the city walls or