During his father's lifetime, Shams al-Din 'Ali entered the service of the Timurid Shah Rukh as a military commander.
In 1414–15 he led the Mihrabanid army and assisted Shah Rukh's forces in putting down a rebellion in Fars.
Shams al-Din traveled to Shah Rukh's court and was confirmed as malik of Sistan.
Shah Rukh defeated the army of the Turkmen leader Qara Iskander and occupied Azerbaijan and Armenia in 1421.
In addition to building irrigation canals, he began the construction of a new city intended to serve as his capital at the end of 1422.