Latin Empire different from Roman Empire
areas of Greece, divided into vassal fiefs:
the Kingdom of Thessalonica
the Principality of Achaea
the Duchy of Athens
the Duchy of the Archipelago
the short-lived Duchy of Philippopolis in north ThraceFurther duchies were projected in Asia Minor, at Nicaea (for Louis of Blois), Nicomedia (Thierry de Loos), Philadelphia  (Stephen du Perche), and Neokastra. These duchies remained theoretical, due to the establishment of the Empire of Nicaea in the area. Nicaea itself was never occupied and Louis of Blois was killed in 1205. Thierry de Loos was captured by the Nicaeans in 1207 and, although released, left the Latin Empire two years later. After a brief Nicaean reconquest, Nicomedia returned to Latin control, but the ducatus Nichomedie remained part of the Imperial domain.  Philadelphia never came under actual Latin control, although the Latin emperor Henry of Flanders laid claim to the region after defeating the local strongman, Theodore Mangaphas, in 1205. The duchy of Neokastra (ducatus Novi Castri) on the other hand was never accorded to a single holder, but was divided among the Knights Hospitaller (one quarter) and other feudatories. The term "duchy" in this case reflects the earlier Byzantine use of the term thema, usually governed by a doux, to designate a province.The Doge of Venice did not rank as a vassal to the Latin Empire, but his position in control of three-eighths of its territory and of parts of Constantinople itself ensured Venice's influence in the Empire's affairs. However, much of the former Byzantine territory remained in the hands of rival successor states led by Byzantine Greek aristocrats, such as the Despotate of Epirus, the Empire of Nicaea, and the Empire of Trebizond, each bent on reconquest from the Latins.
The crowning of Baldwin I (16 May 1204) and the establishment of the Latin Empire had the curious effect of creating five simultaneously existing entities claiming to be successors of the Roman Empire: the Latin Empire, the Holy Roman Empire, and the three remnants of the Byzantine Empire, the Despotate of Epirus, the Empire of Nicaea, and the Empire of Trebizond. None of these polities actually controlled the city of Rome, which remained under the temporal authority of the Pope.