Yasmah-Adad's administrative district bordered the state of Yamḫad and the Syrian steppe (inhabited by semi-nomadic peoples).
His father controlled the northern part of the kingdom from Shubat-Enlil, and his older brother, Ishme-Dagan, ruled over the southeast area from Ekallatum.
In one instance, to facilitate a military alliance with the western Syrian city-state of Qatna, an ally in the fight against the enemy state of Yamkhad, Shamshi-Adad I arranged for his son's marriage to Princess Beltum, the daughter of the king of Qatna, Ishi-Adad.
Shamshi-Adad I was angry with Yasmah-Adad for his refusal to follow orders, and forced him to keep Beltum by his side in the palace.
[5] Some argue that this instance of control demonstrated the extent of power Shamshi-Adad I had over his sons and his kingdom in general.
[6] The correspondence between the father and sons was found in the archives of the city of Mari and provides an interesting and at times humorous look into the dynamics of this family.
Yasmah-Adad was ridiculed frequently by both his brother Ishme-Dagan and his father, and accused of inactive leadership over his district.
"[10] Another example of the complicated, strained relationship between the brothers is found in a letter by Yasmah-Adad to Ishme-Dagan: "Thus (speaks) Yasmah-Addu, Your son.
(ARM 1.108: Dalley 1984;34)[11] Historical opinion of Yasmah-Adad revolves mainly around these letters, the most abundant primary sources about him.
The criticism may reflect the stress that Shamshi-Adad I felt as his newly formed empire began to crumble, considering, as Yasmah-Adad points out in this letter, that his father appointed Yasmah-Adad as a chief ruler of Mari, one of the largest urban centers, as well as one of the most disputed in his kingdom, when one of his generals could have filled the position.
Letters between Yasmah-Adad and Shamshi-Adad I show the role he played in his father’s brutal expansionist military campaign of 1781 B.C.E., particularly in regards with the Ya’ilanum tribe.
This message from Ishme-Dagan I, his brother requests Yashmah-Adad to share the medical expertise with his physician before returning him.