1204 CE - 1222 CE: Reign of Theodore I Laskaris over the Empire of Nicaea.

1204 CE - 1261 CE: The existence of the Empire of Nicaea, the Byzantine Empire in exile.

1206 CE: Theodore I Laskaris proclaims himself emperor of the Byzantine Empire (at this point only the Empire of Nicaea).

1208 CE: Theodore I Laskaris is anointed emperor by the patriarch-in-exile of Constantinople.

1211 CE: Battle of Antioch on the Meander, in which the Nicaean forces of Theodore I Laskaris defeat those of Seljuk Sultan Kaykhusraw I and kill him.

1214 CE: Nicaean Emperor Theodore I Laskaris and Latin Emperor Henry sign the Treaty of Nymphaeum, establishing peace between the two.

1220 CE: The Empire of Nicaea is officially recognized by Venice.

1222 CE - 1254 CE: Reign of John III Doukas Vatatzes of the Empire of Nicaea.

1230 CE: Battle of Klokotnitsa, in which the Bulgarian army under Tsar Ivan Asen II defeated Theodore Komennos Doukas, Despot of Epirus.

1241 CE: Death of Tsar Ivan Asen II.

1242 CE: The Empire of Thessalonica is forced to submit as a despotate to the Empire of Nicaea.

1242 CE: John III Doukas Vatatzes conquers the city of Thessalonica.

1246 CE: The Empire of Nicaea conquers Thessalonica.

1250 CE: Death of Holy Roman Emperor Frederick II.

1254 CE: Death of John III Doukas Vatatzes.

1254 CE - 1258 CE: Reign of Theodore II Laskaris over the Empire of Nicaea.

1258 CE - 1261 CE: Reign of John IV Laskaris over the Empire of Nicaea.

1259 CE: Battle of Pelagonia: Manfred of Sicily and William II of Villehardouin are defeated by the Empire of Nicaea. William is forced to cede the castles of Mystras, Maina, and Monemvasia.

1259 CE: Michael VIII Palaiologos makes himself co-emperor in Nicaea with John IV Laskaris.

1259 CE: Battle of Pelagonia, in which Michael VIII Palaiologos of the Empire of Nicaea defeated the combined forces of Sicily, the Latin Empire, the Latin kingdoms in Greece, and the Despotate of Epiros.

1261 CE: Treaty of Nymphaeum, in which the Byzantine Empire grants Genoa mercantile concessions in exchange for naval support.

1261 CE: The Nicaean general Alexios Strategopoulos sneaks into Constantinople and recaptured it for the Empire of Nicaea.

1261 CE: Michael VIII Palaiologos enters Constantinople and re-establishes it as the Byzantine capital.