What happened on this land around c. 400–500 CE?

Intense warfare with Byzantium; internal reforms and flourishing arts/architecture; strategic exhaustion prior to the 7th century.
Rulers
Sasanian Empire (peak)
4th–7th centuries CE
Sasanian state reaches cultural and political height under several powerful rulers.
Battles
Byzantine–Sasanian War (final great war)
602–628 CE
Exhausting conflict that weakened both empires on the eve of the Arab conquests.