Bactria was a
satrapy of the
Achaemenid Empire. The first mention of Bactria comes in 520 BCE at the
Behistun inscription. Bactria was a special satrapy in that it was ruled by a crown prince or an intended heir. The capital of Bactria was
Bactra, and the region also sometimes included
Sogdia. During the reign of
Darius the Great, the
Bactrians and the Aeglians were placed in one tax district, which was supposed to pay 360 talents every year.