The prince André Kourbski (1528 - 1583) was a close friend and a large general of the tsar Ivan the Terrible before becoming one of his more savage opponents. Its correspondence with the tsar, after his exile in Poland, is a single source of the history of Russian XVIe century.

Kourbski belongs to the family of the Riourikides and its name comes from the village of Kourba, close to Iaroslavl. Very early, it is made recognize by its courage at the time of the annual campaigns of Ivan IV against the khanat of Kazan. In 1553, it orders the right wing of the army at the time of the seat of this city but it is wounded during the battle. In 1555, it crushes the rebellion of the Oudmourtes. It then becomes one of the most listened advisers of the sovereign who inserts it in the caste of the boyards.

In 1560, Ivan IV, wishing to move back its borders until the the Baltic, declares the war against the Livonie. Andre Kourbski order the troops which seize Fellin. But it is already the end of their friendship. In 1564, it flees Russia and is exiled in Lithuania. In its future correspondence with the tsar, it reproaches him for repressing the boyards wrongfully and for oppressing the Polish peasants. On its side, Ivan shows it treason and of disloyalty. It would have tried, according to him, to make of Iaroslavl an independent principality. It would have also tried to allure his wife, the tsarina Anastasia Romanovna Zakharine then to have poisoned it.

The same year, the prince Kourbski leads an army against Russia. Like reward, the Polish king gives him the town of Kovel in Volhynie. He lives there until his death, defending the orthodoxe faith there his Polish subjects.

It is between 1564 and 1579 that André Kourbski and Ivan the Terrible exchanges their increasingly vitriolic letters. The prince blames the tsar for his foolish crimes and decides for a more moderate monarchy. He recommends a devolution to Polish, where the boyards would have their word to say on the policy of the sovereign.