Never ruling as an independent monarch, Rustam Mirza is primarily associated with his governance over the city of Isfahan, which he gained and lost multiple times in the power struggles following Timur's death.
[3] Following Timur's death in 1405, a power struggle erupted amongst his descendants,[2] though the sons of Umar Shaikh were at least nominally now under the suzerainty of their uncle Shah Rukh.
In April 1406, they allied themselves with Rustam's brothers Pir Muhammad and Iskandar and launched a combined assault against Abu Bakr.
Instead, the resistance was led by one of the prince's close advisers, Qadi Ahmad Sa'idi, who managed to forestall Abu Bakr, resulting in the siege being abandoned.
Pir Muhammad attacked Isfahan, though upon failing to capture it, ravaged the surrounding lands by destroying crops, burning houses and breaking dams.
Instead, they resolved to plunder eastern Fars, from Niriz to Darabjirdb, an act in which they were aided by some of their brother's renegade followers, including several governors.
[9] When Shah Rukh marched against Iskandar in 1414/15 after the latter revolted, Rustam and their other brother Bayqara accompanied their uncle in his baggage train.