Joachim III of Bulgaria

In Constantinople Joachim established contacts with the future Pope Nicholas IV, the leader of the western delegation, and it is likely that initially he was inclined to support a union between the two Churches.

[1] However, the Bulgarian empress-consort Maria Palaiologina Kantakouzene (r. 1269–1279), a niece of Michael VIII and in a lifelong feud with her uncle, urged the Church to oppose the Byzantines, who were inclined to negotiate with the Catholics.

[3][4] The Patriarch refused to allow George Terter I to the church sacraments until he conceded to abandon Kira Maria and remarry his first wife, after he secured her return from Byzantine captivity in 1282.

[1][5][6] In 1291 Pope Nicholas IV sent a letter to Joachim III, dated 23 March, reminding the Bulgarian Patriarch of their old friendship and urging him to join the Roman Church.

Despite some hesitations Joachim III maintained the firm position of the Bulgarian Orthodox Church on the matter and the papal initiative failed to produce any tangible results.

[9] In 1299 he crowned the Mongol Chaka, son of Nogai Khan, who fled to Tarnovo in the company of Theodore Svetoslav as a result of a civil war in the Golden Horde.

Historians Ivan Bozhilov and Vasil Gyuzelev speculate that the Patriarch was among the responsible dignitaries for a Mongol invasion in 1285, after which Theodore Svetoslav had to be sent a hostage in the Golden Horde.

[18] ^ a: George Terter married Kira Maria in 1279 after her brother Ivan Asen III seized the Bulgarian crown with Byzantine support during the chaos caused by the Uprising of Ivaylo.