His forces engaged in battle with the Chagataiid troops; an Ilkhanid army that had crossed the Oxus joined the fighting and secured victory for Yasa'ur.
Amir Husain (the father of Hasan Buzurg, who founded the Jalayirid dynasty in Baghdad) was sent to deal with Yasa'ur.
The Amir Coban, overestimating the strength of Yasa'ur, also planned to march against the Chagataiid prince at the head of a 20,000-strong army, but eventually decided to defend against Uzbeg's forces.
The siege of Herat was unsuccessful, however, as upon hearing of the approach of the Ilkhanid army Yasa'ur withdrew into southern Afghanistan.
Yasa'ur's personal troops eventually formed the basis of the Yasa'uri, a group that gained influence within the Chagatai ulus in the mid-fourteenth century.