Here's a great review of the Ayssruian Empire from Marian Feldman for TedEd .
The Assyrians developed the first true empire long before the Mongols or the British and developed innovations like efficient administrartion, constant innovation, and excellent infrstructure that continue to live on.
They conquered a territory that included much of the Middle East and were known as militry innovators and merciless conquerors. They used siege tactis and cruel punishments.
Edleman suggests that the growth of the Assyrian Empire was partly due to their strategy of deporting local populations amd moving them around to fullfill specific needs.