Question

ow did political turmoil contribute to the decline of the Byzantine Empire

Answer 1

It robbed the empire of valuable leadership as incompetent rulers weakened its administration of the military, making it unable to respond to threats from either the rising power of the Ottomans or even that of Italy's city-states such as Venice. As the empire weakened, the West grew stronger.

They also made it vulnerable to political enemies within who wanted to grab more power for themselves and outside its borders from those subjects that either sought to be free of the Byzantines or were whom the Byzantines had made enemies of. And the Byzantines had many enemies towards the end, often from within their own noble houses.

The most grievous example was the Fourth Crusade. Venice had been insulted and humiliated by the Byzantines who made an example of their trading status within the capital in brutal fashion. When the Fourth Crusade was called up, the army was heavily in debt to Venice which by now had become a powerful city-state built up on trade. To pay off their debt, Dandolo of Venice convinced the Crusaders to sack a the port of Zara to earn back what they owed. Zara was a Venetian port that was taken over by Hungary, so you can see why Dandolo wanted it back under the ruse of paying off what the crusaders owed. Pope Innocent III was outraged and excommunicated the expedition, but it did little to stop what came next.

Philip of Swabia sent a message to the crusaders after they took Zara that told them of how Alexius IV, son of Isaac II and who had fled Constantinople after his brother Alexius III usurped the throne from his father, was in his caretaking after his escape. If they would put him back on the throne, he would supply men and money to help them on their way to Egypt. Dandolo, in his eighties and blind as a bat, still had a razor sharp mind and saw the benefits of taking the deal. The target - Constantinople.

On the premise of restoring Alexius IV to the throne, and the promise of payment, the Crusaders marched on Constantinople in 1204. Even though they were Eastern Orthodox, they were still Christians, but the vengeful Venetians saw only a chance to take back what they had lost and convinced the Crusaders to attack and pillage the city...which they did. Alexius III fled and the Crusaders embarked on an orgy of pillaging, rape, and death as they attacked the city. Holy relics and anything else of worth, icons - so much was melted down and destroyed to provide coin that the Byzantine treasure was still short on to pay their debts.

After that, Alexius IV assumed the throne for barely a year, but the Venetians and their Latin allies had succeeded in humiliating the Byzantine empire and critically weakening it in the face of the rising Muslim empire in the east.

And things would only get worse.