Bobrok

He could have been a junior member of the Rurikid House of Ostrog[1] or a grandson of Gediminas of Lithuania, probably one of Karijotas's sons.

[2] It has also been speculated that he held the village of Bobrka on the Boberka River as a fief from Liubartas.

He led the Muscovite army against Oleg II of Ryazan in 1371 and successfully raided Volga Bulgaria in 1376.

He was in charge of the conquest of Severia in 1379 and was in command of a regiment lying in ambush during the great Battle of Kulikovo in 1380.

Valentin Yanin has speculated that he took the tonsure after his son had been killed by a fall from a horse.

Bobrok's ambush regiment . A miniature from the Illustrated Chronicle of Ivan the Terrible .