Emperor Heraclius defended the Byzantine Empire from the Persians but lost the reconquered land to the Arabs shortly after.
The Byzantine-Arab wars wrought havoc on the Byzantine Dynasty but led to the creation of the highly efficient military theme system.
The Isaurian dynasty is characterized by relative political stability, after an important defeat of the Arabs by Leo III, and Iconoclasm, which resulted in considerable internal turmoil.
The Byzantine Iconoclasm was the banning of the worship of religious images, a movement that sparked internal turmoil.
Irene of Athens, the first woman Emperor of the Byzantine Empire, fought for recognition as Imperial leader throughout her rule and is best known for the ending of Iconoclasm in the Eastern Church.