The qurbūtūs appear to have originated as royal bodyguards. Accounting lists documenting the distribution of wine rations reveal that in the early ninth century BC between a few dozen and a few hundred qurbūtūs guarded the king and had their own chariots and cavalry. Inscriptions in fact occasionally mention the qurbūtūs marching at the vanguard of the army on campaign alongside the king.
Sargon II (r. 722-705 BC) appears to have massively expanded the to a force acted in a way akin to a secret police or political commissars. The king would often entrust a with delivering his sealed orders and seeing that they were carried out. The kept a watchful eye on the governors and vassal kings who together governed the Assyrian Empire and reported any suspected disloyalty back to the king.
