Sultan Mohammed Öz-Beg, better known as Uzbeg or Ozbeg (1282–1341, reign 1313–1341), was the longest-reigning khan of the Golden Horde, under whose rule the state reached its zenith. He was succeeded by his son Jani Beg.
He was the son of Toghrilcha and grandson of Mengu-Timur, who had been khan of the Golden Horde from 1267-1280.
Öz-Beg, who was in Khwarizm, assumed the throne upon the death of his uncle Toqta in January 1313 with the help of former khan's muslim vizier Temur Qutlugh and Bulaghan (or Bayalun) khatun. At first, Mongol nobles were against him and organized the plot to kill new khan. Uzbeg found out the plot and crushed rebels. His adoption of Islam as a state religion led to a conspiracy of shamanist and buddhist princes, which was severely subdued. He islamicized Gorde Horde and beheaded 70 princes of Chingisids as well as emirs and lamas. Ozbeg found out that his competitor was backed by Yuan envoys of Khagan Ayurbarwada Buyantu and deteriorated his relationship with Yuan Dynasty. Last of his rebel relatives was shamanist khan Ilbasan of White Horde and he was murdered in 1320. Uzbeg installed Mubarak Khwaja who was a muslim in throne of White Horde but he discouraged. In the long run, Islam enabled the khan to eliminate interfactional struggles in the Horde and to stabilize state institutions. Russian scholar Lev Gumilev wrote that the Khanate turned into Sultanate.
He forced the Mongol elite to convert to Islam, but at the same time, he was quite tolerant toward Christians and the local pagans of his empire such as Russians, Circassians, Alans, Bulgars, Finno-Ugric people, Turks and Crimean Greeks as long as they continued to pay the jizyah.
Öz-Beg maintained one of the largest armies in the world, which exceeded 300,000 warriors. He employed his military clout to conduct campaigns against the Ilkhanids in Arran in 1319, 1325 and 1335. Ilkhanid commander Chupan repulsed one of his first two attempts and even invaded deep into Jochid Ulus in 1325. After he found an ally against the Ilkhanids in the shape of Mamluk Egypt, one of Cairo squares was named after him. The khan had the daughter of previous khan's sister, princess Tulunbuya, married with Mamluk sultan. But she died soon after and Uzbek was disappointed. In 1323, a peacy treaty was signed between Egypt and Ilkhanate. The situation relieved the alliance and Mamluks refused mannerly to invade Ilkhanate. Ozbeg's next incursion was coincided with Abu Said's death. However, the weather turned bad and new Ilkhan Arpa Ke'un came with a large force to face full of his army. His army had to withdrew for those reasons.
Chagatai Khan Esen Buqa I attempted to gain the support of Uzbeg Khan against Emperor Buyantu in 1313 and 1316. Esen buqa warned him that the Emperor would overthrow Uzbek and install another khan from Jochids. But Uzbek's vizier convinced him not to believe his words and the Khan refused to help him. Although, he tried his best to eliminate every influence and inspiration of Yuan Dynasty on Jochid Ulus, the Khan's diplomatic relationship with Kublaids improved in 1324. By 1330's, Ozbeg had begun sending tributes to Mongol Yuan Emperors and received his share from Jochid possessions in China and Mongolia in exchange.
Öz-Beg was engaged in wars with Bulgaria and Byzantine from 1320 to 1332. His attempt to reassert Mongol control over Serbia was unsuccessful in 1330. Emperor Andronikos III gave his illegitimate daughter in marriage to Uzbek but relations turned sour at the end of Andonicus's reign and the Mongols mounted raids on Thrace between 1320 to 1324, until the Byzantine port of Vicina Macaria was occupied by the Mongols. Andonicus's daughter, who adopted the name Bayalun, managed to escape to Byzantine Empire due to fearing islamic conversion.
Ozbeg allowed Genoese, who harassed by Tokhta, to settle in Crimea. But the Mongols sacked Sudak under Khan Ozbeg in 1322 as a result of a clash between Christians and Muslims in the city. The Genoese merchants in the other towns were not molested in 1322. The Pope intervened and asked Ozbeg to restore Roman Catholic churches destroyed. Ozbeg was friendly towards the Pope and exchanged letters and gifts. Khan Ozbeg signed a new trade treaty with the Genoese in 1339 and allowed them to rebuild the walls of Kaffa. In 1332 he had allowed the Venetians to establish a colony at Tana on the Don.
During the reign of Uzbeg, Sarai was more quickly becoming a main commercial center and industrial trading center of the country than just a political center. The expression of Mongol camp mentality, following Ash and the nearby absence of some structures.
For successfully expanding Islam, it was necessary to build a mosque and other "elaborate places;" requiring baths—an important element of Muslim culture. Sarai attracted merchants from European, Asian and Islamic countries as well as Middle East. Slave trade flourished due to strengthening ties with Mamluk Sultanate. Successful commercial revolutions require new markets, caravans, a "place where merchants find their way." Growth of wealth and increasing needs of production always produce population growth, this did not passover Sarai. Dwelling places of the region increased. This transformed the capital into a center of a large Muslim government, giving it the appropriate aspect and status. Uzbeg actually came to build a new city, which received the official name Saray al-Jedid or New Sarai.
As regards Russian politics, Öz-Beg supported the earliest princes of Muscovy - his brother-in-law Yury of Moscow and Yury's successor Ivan Kalita - against the westward-leaning Princes of Tver. Three of these - Mikhail of Tver, his son Alexander and grandson Theodor - were killed in Sarai at Öz-Beg's behest.
In 1317, Mikhail Yaroslavich defeated Yuri at a village called Bortenevo. Mikhail captured Yuri's wife, who was the Khan's sister. Unluckily, Yuri's wife died when she was in the custody of Mikhael. He was summoned to the court of Golden Horde and beheaded in December of 1318.
Although, Ozbeg's army killed Lev II and Andrew of Galicia in 1323, the Grand Duchy of Lithuania and the Kingdom of Poland had a great influence on Galicia-Volhynia. Lithuanians defeated rus' boyards and occupied Kiev and its surrounding areas in 1330. As a result of losing direct rule over Kiev, Wallachia and its ruler Basarab I had become de facto independent from Ozbeg since 1324. But Ozbeg was still able to threaten Byzantine, Lithuania and Bulgaria.
Following Yury's machinations which led the khan to grant the yarlik to Moscow and their father's execution at the Horde, Dmitry killed Yuri in Sarai four years later. Ozbeg waited to punish Dmitri, however, he arrested the prince of Tver for the murder and executed him in 1326.
When the Khan's cousin, the Baskak Shevkal and his Tatars were killed in Tver and a rebellion erupted there, Alexander Mikhailovich fled to Pskov to escape a punitive expedition of 50,000 Mongol-tatars , which was headed by his cousin Ivan Daniilovich. Tver's uprising against the Horde was bloodily suppressed by Muscovite and Tatar forces in 1327. But Aleksandr traveled to the horde with tribute and was given the yarlik to Tver in 1337. The Khan pardoned him. Unfortunately, his enemy Ivan again set the Horde's Khan against him with the aid of intrigue. Alexander Mikhailovich was summoned to the Horde again and was executed at the hand of Khan Uzbek. Tver, was pillaged and many of its citizens massacred and Ozbeg appointed Ivan the Grand Duke of Vladimir. That was the beginning of the rise of Muscotives.
Ozbeg welcomed Ivan's sons and made Simeon Grand prince (duke) in 1340. Simeon was given more powers by the Khan to counter Lithuania's growing power. And Ozbeg launched military expeditions into Lithuania that threatened Mongol dominance in Russia.