It is for this reason that upon the death of Sadun in 1282, Demetrius refused the post of atabeg to his son Khutlubuga and made him a sworn enemy.

Although he continued to be titled "king of Georgians and Abkhazians, etc", Demetrius's rule extended only over the eastern part of the kingdom.

Demetrius also participated in the Mongol campaigns in the Middle East against the Mamluks of Egypt and particularly distinguished himself with Beka I Jaqeli at the head of a Georgian army of 15,000 men under the orders of Möngke Temür, brother of Abaqa Khan, during the Second Battle of Homs in 1281.

The same year, Arghun revealed a plot organized by his powerful minister Buqa, whose son was married to Demetrius's daughter.

Bugha and his family were massacred, and the Georgian king, suspected to be involved in a plot, was ordered to the Mongol capital, or Arghun threatened to invade Georgia.