When the Persians realized that the Greeks had began to retreat from their positions the previous night they launched an attack. In the resulting battle the Persians were defeated with heavy loss and their commander Mardonius killed.
Colorful indeed. I found that if the Persians can survive long enough to keep that line of archers in the rear until the 'crisis', they can use this de facto reserve to telling effect.
This snipping tool capture represents the end result of one game with the Persians victorious: