Conflict with Mikhail of Tver
After his father Daniel died in 1303, Yury became prince of Moscow, and contended over the title of grand prince of Vladimir (the supreme position among princes in the northeast) with his uncle Mikhail of Tver. Because Daniel had never been grand prince of Vladimir, his descendants, including his son Yury, had no legitimate claim to the throne of Vladimir according to traditional succession practices. This is why the Golden Horde's khan, Tokhta, granted Mikhail of Tver the grand princely title when Andrey of Gorodets died the next year on 27 July 1304. Mikhail went to the Golden Horde's capital city Sarai, where the khan elevated him grand prince. His nephew Yury rebelled against this appointment, but two military campaigns by Mikhail of Tver against Moscow in 1305 and 1308 forced Yury to comply with the khan's decision. The Tverian army besieged Pereslavl and Moscow itself.
In the meantime, Yury arranged the murder of Prince Konstantin of Ryazan. This unlucky ruler had been captured by Yury's father back in 1302 and had been incarcerated in Moscow since then. While Ryazan was shocked by such a barbarity, Yury annexed the key Ryazanian fortress of Kolomna to Moscow. He also captured Mozhaisk, which formerly belonged to the princes of Smolensk. By 1314, Yury secured backing from the Metropolitan Peter and formed a military alliance with Novgorod against Tver. Now, he felt strong enough to challenge Mikhail of Tver in the Horde.
In 1315, Yury went to the Golden Horde and, after spending two years there, constructed an alliance with Uzbeg Khan. Yury married the khan's sister Konchaka, a Tatar princess who converted to Russian Orthodox Christianity for her marriage to Yury, and adopted "Agafiia" as her baptismal name. Uzbeg Khan deposed Mikhail and nominated Yury as the Grand Prince of Vladimir. Back in Moscow with a large force of Tatars, Yury approached Tver. However, Yuri's army was defeated and his brother Boris and his wife were taken prisoners. Thereupon he fled to Novgorod and sued for peace. At that time his wife, still held in Tver as a hostage, died unexpectedly. Yury availed himself of the confusion that followed and announced to the khan that she had been poisoned on Mikhail's order. Uzbeg Khan summoned both princes to Sarai and, after a trial, had Mikhail executed on 22 November 1318. Yury, who both depended on and benefited from Uzbeg Khan's favour, was allowed to be the grand prince of Vladimir for the next four years (1318–1322).
