Upon receiving news of his father's death, Simeon and his brothers Andrey and Ivan left for the Golden Horde to seek Uzbeg Khan's patent (yarlyk) for taking over the title of Grand Prince.

[3] He was also granted the ceremonial title epi trapezes offikios (Ancient Greek: ὁ ἐπί τραπέζης ὀφφίκιος) by the Byzantine Empire,[5] which can be loosely translated as seneschal or stolnik.

Simeon and metropolitan Theognostus hastily organized a coalition of princes against Novgorod, claiming that "They [Novgorodians] make war and peace with whomever they please, consulting no one.

Novgorod Republic accepted the fact and ceded all taxes from Torzhok area, estimated at 1,000 roubles in silver annually, to Simeon who agreed to honor the existing civic charter.

[7] Uzbeg Khan, Simeon's sovereign, died soon afterwards; his successor, Jani Beg, secured the control of the Horde through killing his brothers.

Simeon, whose title of Grand Prince obliged him to protect Novgorod, was reluctant to do so, as if expecting the weakened republic to collapse for his own benefit.

Simeon preferred to sign a truce with Algirdas, releasing the prisoners and securing marriages between Lithuanian princes and Russian brides.

The marriage of pagan Algirdas to Orthodox Uliana of Tver, unlawful from the viewpoint of the church, was nevertheless approved by Theognostus; it gave birth to Jogaila.

[citation needed] He installed Alexis as Metropolitan of Moscow, successor to the late Theognostus, and secured a profitable estate for Maria.