Muzaffarids in 1347. He unsuccessfully besieged Yazd (1350–1351), after which his fortunes declined rapidly. Defeated on the field in 1353, Abu Esshaq was forced to take refuge in Shiraz and finally surrender. He managed to escape from Shiraz and fled to Isfahan, but Mubariz al-Din pursued him, took the city and executed the Injuid ruler. Fars and western Iran were now under his control. With the destruction of Injuid authority, the Muzaffarids were the strongest power in central Iran, and Shiraz was made their capital. Mubariz al-Din's strength was such that when the khan of the Golden Horde, Jani Beg, sent an offer to make him a vassal, he was able to decline. In fact, he pushed on into Azerbaijan, which Jani Beg had conquered in 1357. He defeated the khan's governor Akhichuq and occupied Tabriz, but realized that he could not hold his position against the Jalayirid troops marching from Baghdad and soon retreated. The Jalayirids would therefore maintain a hold on Tabriz, despite further attempts by the Muzaffarids to take it. Mubariz al-Din was known as a cruel ruler, and soon afterwards 1358, his son Shah Shoja blinded and imprisoned him. A temporary reconciliation was reached, but it failed to last and he died, again in prison, in 1363. Reign of Shah Shoja Shah Shoja proved to be a less of a tyrannic figure, but he was constantly fighting with his brothers, causing a long period of instability. In 1363 he marched against his first brother Shah Mahmud, who had been given control of Isfahan, although a peace was soon brokered. In the following year however, Shah Mahmud, with the support of his father-in-law Shaikh Uvais of the Jalayirids, invaded Fars and captured Shiraz. Shah Shoja would not be able to reconquer his capital until 1366. Shah Mahmud would continue to play and influential role in Iranian politics, using his marriage alliance to claim Tabriz from the Jalayirids after Shaikh Uvais died in 1374. He occupied the city but soon gave up after he was struck by illness. He died the next year, allowing Shah Shoja to occupy Isfahan. Shah Shoja then marched on Tabriz himself, but was forced to turn back when internal conditions in Fars deteriorated. His second brother Shah Muzaffar's son, Shah Yahya, rose in revolt in Isfahan. Having to make peace with the Jalayirids, Shah Shoja offered to marry his son Zain Al-Abidin to