Mahmud repaired irrigation systems and implemented a tax reform, probably the
model for that of Yeh lii Ch'u ts'ai in China, with a poll tax on adult males called qubchur and a land tax called qalan. Other taxes were abolished, at
least in theory. Mahmud had to contend with attempts by Chaghadai, whose
territory adjoined Transoxania, to assert authority. In 636/1238^ the rebellion of Mahmud Tarabi in Bukhara brought a punitive assault, but Mahmud was able to prevent a massacre by an appeal to Ogedei. Perhaps to placate Chaghadai, Ogedei moved Mahmud to China and replaced him by his son Masud, with no change in policy. Contemporary observers and numismatic evidence suggest that by 1260 Central Asia had nearly regained its earlier
prosperity. 2 The situation was very different in Iran, where Chinggis Khan made no attempt to install systematic administration. 29 Some eastern cities had Mongol officials but most simply remained under earlier rulers: the atabegs of Fars in southern Iran, the Khwarazm Shah's son Ghiyath al Din in Rayy, and in Azerbaijan, the Saljuqid atabegs. Kirman was seized in 619. by Baraq Hajib, a former servitor of the Khwarazm Shahs, who gave allegiance to the Mongols and founded the Qutluq Khanid dynasty. Most rulers offered submission to the qaghan and many travelled to the central court.