It appears that among the terms of the peace concluded in A.D.442 between Isdigerd II.

and the younger Theodosius, the Romans had undertaken to pay annually a certain sum of money as a contribution towards the expenses of a fortified post which the two powers undertook to maintain in the pass of Derbend, between the last spurs of the Caucasus and the Caspian.

This fortress, known as Juroi-pach or Biraparach, commanded the usual passage by which the hordes of the north were accustomed to issue from their vast arid steppes upon the rich and populous regions of the south for the purpose of plundering raids, if not of actual conquests.
Their incursions threatened almost equally Roman and Persian territory, and it was felt that the two nations were alike interested in preventing them.

The original agreement was that both parties should contribute equally, alike to the building and to the maintaining of the fortress; but the Romans were so occupied in other wars that the entire burden actually fell upon the Persians.

These latter, as was natural, made from time to time demands upon the Romans for the payment of their share of the expenses; but it seems that these efforts were ineffectual, and the debt accumulated.