The Strongest rival of Byzantine Empire

thast a hard one for me. From what i know you have the sassanids battle it out toe to toe for quite a while .weakened from this and (the plague?) they get hammered by the newly mobilise and converted islamic armies. after all of these set backs did the turks come in and take the rest.

so ill say, the sassanids becase they battle it out much harder for much longer

but then agian the latins had the knife for the back, very dangerous......

       

I voted for Papacy. I think that it was not only the strongest rival Byzantine eimpre have met, but also the main who provoked its colapse.

This is a rather tough question, seeing as Byzantium endured for roughly a thousand years, and in that time many mighty challengers came and went.

The Bulgars are a good example of this, who during the reign of Khan Krum (d. 814) and his followers were quite the threat, but later faded into obscurity. The Visigoths, Ostrogoths and the Vandals were just passing threats, comparatively speaking. The Sassanids too had their burst of conquest, until Heraclius' campaign shattered their power, then they too faded in favour of the Arabs. The Arabs, unlike many others, managed to conquer and hold about half of the Empire's land. Their incursions in Anatolia and attempts at Constantinople, however, seem rather futile. The Seljuks were the first to make seriously alarming progress, after they overran most of Anatolia there really wasn't much "empire" left. The Crusaders managed to push the Seljuks temporarily back, but they also pushed the Byzantines back in many ways, especially in 1204. The Papacy is an interesting suggestion, I don't feel they were much of threat other than on the religious level though, Innocent III never meant for the 4th Crusade to make stops in Dalmatia and Constantinople. Lastly, the Ottomans did finish the Empire off, but to it seems a bit unfair to give them much credit for the defeat of someone already defeated, at this point the military and financial power of Byzantium was a laughing matter in Christendom.