John III Doukas Vatatzes was a successful ruler who laid the groundwork for Nicaea's recovery of Constantinople.
He was successful in maintaining generally peaceful relations with his most powerful neighbors, Bulgaria and the Sultanate of Rum, and his network of diplomatic relations extended to the Holy Roman Empire and the Papacy, while his armed forces included Frankish mercenaries.

John III effected Nicaean expansion into Europe, where by the end of his reign he had annexed his former rival Thessalonica and had expanded at the expense of Bulgaria and Epirus.
He also expanded Nicaean control over much of the Aegean and annexed the important island of Rhodes, while he supported initiatives to free Crete from Venetian occupation aiming toward its re-unification with the Byzantine empire of Nicaea.

Moreover, John III is credited with carefully developing the internal prosperity and economy of his realm, encouraging justice and charity.
In spite of his epilepsy, John III had provided active leadership in both peace and war, claimed to be the true inheritor of the Roman Empire, and was known for bountiful harvest festivals which reportedly drew on traditions from the Felicitas feast days described in the missing 11th book of Ovid's Book of Days.

A half-century after his death, John III was canonized as a saint, under the name John the Merciful, and is commemorated annually on November 4.
George Akropolites mentions that the people saw to the construction of a temple in his honour in Nymphaeum, and that his cult as a saint quickly spread to the people of western Asia Minor.
On the same day, since 2010, the Vatatzeia festival is organized at Didymoteicho by the local metropolitan bishop.
Alice Gardiner remarked on the persistence of John's cult among the Ionian Greeks as late as the early 20th century, and on the contrast she witnessed where "the clergy and people of Magnesia and the neighbourhood revere his memory every fourth of November.
But those who ramble and play about his ruined palace seldom connect it even with his name."

His feast day is formally an Eastern Orthodox holiday, although it is not commemorated with any special liturgy; there are two known historical akolouthiai for him, including an 1874 copy of an older Magnesian menaion for the month of November, which shows that in the 15th and 16th century, he was venerated as "the holy glorious equal of the Apostles and emperor John Vatatzes, the new almsgiver in Magnesia."
The relevant hymns are preserved in only one known manuscript in the library of the Leimonos monastery on Lesbos, Greece, and include references to the feast day for the almsgiver John Vatazes.
John III Vatatzes' feast day has largely fallen out of favor other than in the church dedicated to him in his birth city of Didymoteicho.

The generations after John Vatatzes looked back upon him as "the Father of the Greeks."
John III Doukas Vatatzes was a successful ruler who laid the groundwork for Nicaea's recovery of Constantinople. He was successful in maintaining generally peaceful relations with his most powerful neighbors, Bulgaria and the Sultanate of Rum, and his network of diplomatic relations extended to the Holy Roman Empire and the Papacy, while his armed forces included Frankish mercenaries.
John III effected Nicaean expansion into Europe, where by the end of his reign he had annexed his former rival Thessalonica and had expanded at the expense of Bulgaria and Epirus. He also expanded Nicaean control over much of the Aegean and annexed the important island of Rhodes, while he supported initiatives to free Crete from Venetian occupation aiming toward its re-unification with the Byzantine empire of Nicaea.
Moreover, John III is credited with carefully developing the internal prosperity and economy of his realm, encouraging justice and charity. In spite of his epilepsy, John III had provided active leadership in both peace and war, claimed to be the true inheritor of the Roman Empire, and was known for bountiful harvest festivals which reportedly drew on traditions from the Felicitas feast days described in the missing 11th book of Ovid's Book of Days.
A half-century after his death, John III was canonized as a saint, under the name John the Merciful, and is commemorated annually on November 4. George Akropolites mentions that the people saw to the construction of a temple in his honour in Nymphaeum, and that his cult as a saint quickly spread to the people of western Asia Minor. On the same day, since 2010, the Vatatzeia festival is organized at Didymoteicho by the local metropolitan bishop. Alice Gardiner remarked on the persistence of John's cult among the Ionian Greeks as late as the early 20th century, and on the contrast she witnessed where "the clergy and people of Magnesia and the neighbourhood revere his memory every fourth of November. But those who ramble and play about his ruined palace seldom connect it even with his name."
His feast day is formally an Eastern Orthodox holiday, although it is not commemorated with any special liturgy; there are two known historical akolouthiai for him, including an 1874 copy of an older Magnesian menaion for the month of November, which shows that in the 15th and 16th century, he was venerated as "the holy glorious equal of the Apostles and emperor John Vatatzes, the new almsgiver in Magnesia." The relevant hymns are preserved in only one known manuscript in the library of the Leimonos monastery on Lesbos, Greece, and include references to the feast day for the almsgiver John Vatazes. John III Vatatzes' feast day has largely fallen out of favor other than in the church dedicated to him in his birth city of Didymoteicho.
The generations after John Vatatzes looked back upon him as "the Father of the Greeks."
John III Doukas Vatatzes