After a successful resistance in Asia Minor, Theodore I Laskaris founded the Empire of Nicaea and laid claims to the Byzantine throne, along with the Angelos family of Epirus and the Komnenoi of Trebizond.

[2] The Byzantine Greek population of Asia Minor sought refuge to Theodore's empire, which gradually acquired control over much of western Anatolia.

[7] According to the Oxford Dictionary of Byzantium, the "most probable" etymology is the one proposed by B. Hemmerdinger in 1969, according to which the name derives from the Persian word Lashkarī (لشگری, also Arabic: عسکری, ʿaskarī), meaning "warrior, soldier".

According to other accounts, Theodore had left before the fall of the city, right after he escaped from prison sometime before September 1203; he then moved to Asia Minor with a small group of trusted soldiers and his close family.

[24][25] Whatever the case, Constantine had no option but to quickly flee the capital and on the following day of the sack he sailed to the Asian side of the Bosporus strait.

[27] Meanwhile, in Asia Minor the Latin rule found resistance by local Greek magnates trying to transform their estates into autonomous units.

[35][36] Theodore had to defend his empire not only against the Crusaders but also against David Komnenos, a rival Greek emperor in Trebizond to the east on the Black Sea.

[37] During his reign Laskaris undertook the task of expanding the borders of his empire, facing the forces of the Latins and the Seljuks on several occasions, while at the same time he laid the foundations of the internal administration of the newly formed state.

[41] Vatatzes had to fight off a rival claim by Theodore's brothers, Isaac and Alexios, who fled to the Latin Empire and sought aid in order to depose him.

Nevertheless, Vatatzes' victory at Poemanenum in 1224 was decisive; it strengthened his own position and heralded a long and successful Nicaean offensive against the Latin holdings.

[42] Throughout his reign, Vataztes' main rivals were the Bulgarian tsar Ivan Asen II and the Latin rulers of Constantinople to the west, as well as the Sultanate of Rum to the east.

[43] Under the reign of Vatatzes, the Greeks regained nearly the whole of western Anatolia from the Turks,[36] while the Latin empire was significantly reduced to Constantinople and its surroundings.

[44] Through a series of military victories, successful diplomacy, and beneficial policies, Vatatzes managed to significantly strengthen his empire, while also gaining popularity among the Byzantines, which resulted in his canonization as a saint by the Orthodox Church.

[44] During his four year reign Theodore II initiated a series of reforms aimed at curtailing the role of the aristocratic families in the internal affairs of the state.

[48] Theodore ruled until his death in 1258 leaving his eight year old son John IV Laskaris as the legal heir to the imperial throne.

[49] Mouzalon's lowly origins were viewed with discontent by the Byzantine aristocracy, who was reminded of the Laskarid policy that aimed to regulate their power.

[3][51] In the same year, Michael was in charge of the army that defeated an anti-Nicaean coalition at the battle of Pelagonia, a victory that enabled him to recapture Constantinople in 1261.

[9] The scholars Constantine Lascaris and John Ryndakenos Laskaris were among the emigres who fled the fall of the Byzantine Empire to the Ottomans and found refuge in Italy.

[53] In the past, Guglielmo had been imprisoned following his participation at the battle of Pelagonia against the Byzantines, but he managed to be released thanks to his close connections with the Geneose.