The central element in the making of alliances in the Ancient Near East was the oath. So much so, in fact, that the term for them was often "oath by the god"(nîš ilim) , or in the plural "oath by the gods"(nîš ilî or nîš ilâni). We must carefully distinguish between two types of oath, even if the ancient Mesopotamians did not explicitly make this distinction: purgatory oath on the one hand, and promissory oath on the other. The purgatory oath was used to clear oneself of an accusation; such an oath therefore relates to the past. Accused of plundering a city in the Karana kingdom, Išme-Dagan declared to King Asqur-Addu, with whom he wanted to conclude an alliance:
" Am I not your brother? I'm willing to swear an oath by the god that I'm not the one who pillaged! "
(ARM 26/2 515)
Promissory oaths, on the other hand, involved a commitment to the future. Some were linked to specific circumstances, but most did not refer to particular situations. They could be taken by entire social groups, or by well-defined socio-professional categories such as soothsayers. Oaths taken in the context of alliances are essentially commitments concerning the future, and therefore belong to the category of promissory oaths. What authority could ensure that these promises were kept? In the absence of any legal structure, it was the gods.
The divine guarantee of loyalty and covenant oaths was provided by the gods of both parties. A simple witness kept a record of what had happened, and could be questioned about how the contract had been concluded (whether the prize money had been paid, etc.), but was not responsible for enforcing the agreement. Yet the gods were not supposed to be passive: if the person swearing the oath did not respect it, the divinities were expected to send a sanction. Their role was therefore more that of guarantor than witness. The list of gods invoked in each treaty generally reflects the pantheon of both parties.
