After the reign of Emperor Heraclius and the loss of all of its overseas borders, Byzantine territories were pretty much limited to the Balkans

Balkans

The Balkans is a geopolitical and cultural region of southeastern Europe...

 and Anatolia

Anatolia

Anatolia is a geographic and historical term denoting the westernmost protrusion of Asia, comprising the majority of the Republic of Turkey...

. When Byzantium

Byzantium

Byzantium was an ancient Greek city, founded by Greek colonists from Megara in 667 BC and named after their king Byzas . The name Byzantium is a Latinization of the original name Byzantion...

began to recover after a series of conflicts in the 8th century and its territories stabilized, its population began to recover. By the end of the 8th century there were 7,000,000 Romans, a figure that climbed to over 12,000,000 people by 1025. The numbers began falling steadily to 9,000,000 people at 1204 and even lower to 5,000,000 people at 1281 with the arrival of the Turks.