Pride Goes Before a Fall
Even the strongest of nations will be defeated if it allows arrogance and pride to over-ride its government. Greece did not only wound the armies of Persia with her earlier defeat; Persian pride was wounded as well, and a thirst for revenge is clouding Xerxes' judgement. He also believes that his is an unbeatable foe for the Greeks due largely to the fact that his armies put down rebellions in Egypt and Babylon. This gives him a false sense of reality and makes him think that he can lead his forces to victory over any enemy. Unfortunately, his pride has blinded him to the realities of battle. This is when the ghost of Darius admonishes his son. He tells that he has overweening pride and has been warned by the voice of God to cease attacking Greece.
Mass Grief
As in all Greek tragedies, the Chorus tends to react the most to grief when it occurs in the play. Grief is one of the key themes here; when the Messenger delivers the news of Persian defeat, the chorus begins to lament. This is all the more effective because it would have been a lamentation shared by the Ancient Greek audience who would also have suffered losses during the wars, and would therefore identify with the characters. Several examples of grief are given in the play, for example the widowed bride who grieves for both her lost husband and the loss of her youth and hope for the future.
Revenge
The main reason for the attack on the Greeks is revenge. Xerxes is angry about being vanquished by the Greek armies and lets this anger fester, so that soon it clouds his judgement completely. A sub-theme in the play is that of the foolishness of acting out of revenge, or seeking vengeance. However, Darius tells us that seeking victory out of vengeance can never succeed and only brings more death and loss.
Empire Building
Throughout the play, the different empires are at war with each other and seem unable to coexist in peace for very long. Persia is the main cause of the wars, putting down rebellions with a bloodthirsty hand in Egypt and Babylonia, always wanting to assert its strength over the neighboring nations. This empire building is the cause of the majority of the warring that occurs and is therefore one of the themes of the play.
