<P> Though the Crusades assisted Byzantium in driving back some of the Turks, they went far beyond the military assistance envisaged by Alexios I. Instead of following the strategic necessities of the war against the Turks, the Crusaders were focussed on the quest of re-conquering Jerusalem, and instead of returning territory to Byzantium, the Crusaders established their own principalities, becoming a territorial rival to Byzantine interests in their own right . </P> <P> This was true already during the Third Crusade, which induced emperor Isaac II Angelos to make a secret alliance with Saladin to impede the progress of Frederick Barbarossa, but open conflict between Crusaders and Byzantium erupted in the Fourth Crusade, resulting in the Sack of Constantinople in 1204 . Constantinople was now itself a Crusader state, known as the Latin Empire in historiography, but from the Greek perspective as Frankokratia or "rule of the Franks". Vestiges of imperial power were preserved in minor principalities, the Nicaean Empire, Trebizond and Epirus . Much of the Nicaean Emperors' efforts now went into combating the Latins, and even after Constantinople was returned to Greek rule under the Palaiologoi in 1261, the Empire exerted much of its efforts into defeating its Latin neighbours, contributing to the eventual failure of the Crusades by 1291 . </P> <P> Throughout the 14th and 15th centuries the Empire suffered from many natural disasters, invasions and several coups . </P> <P> A series of societal infighting also weakened the Byzantine Empire's military power . There were two major civil wars during the late Byzantine Empire, one in 1321 another in 1341 . These civil wars also severely diminished the Byzantines' military capabilities . </P>

What changes were made to the roman empire in attempts to slow its decline