Justinians attempts to reconquer western territory left the east open to attacks by Persians and Slavs.
Justinian had come to the throne in 527. War with the Persians began in 540 and continued until a 50-year peace agreement was signed in 561.
The Sclaveni (as the Slavs then were known) gave Justinian problems in the Balkan region.
Belief in the benefits of profiterable trading.
