The Byzantines were able to keep Constantinople safe because they were one of the few peoples living in the time between the fall of Rome and modern days who had a strong government and one that worked. The rest of the Roman Empire had been divided by conquest into a good hundred or more independent units. These were ruled by kings, princes, dukes, marquises, and counts, and some cities were even free republics headed by wrangling priors. Their boundaries were always changing, and nobody ever knew just who was governing whom today, and who would be tomorrow. But the eastern half of the Roman Empire had a single government which was almost always orderly.
The Byzantines were able to do it because they had a fine army, and when they needed it, a swift and deadly navy—to say nothing of a diplomatic corps with a well-paid staff of skillful, highly trained diplomats.
They were able to do it because of their Christianity. After Antioch (in Syria) and Alexandria (in Egypt) had been captured by the Arabs, Constantinople was the most important Christian city except Rome. And as far as the Byzantines were concerned, the state worked for Christianity, and Christianity worked for the state.
Finally, the Byzantine Empire was able to stand firm and to last so long because the Byzantines could afford to spend what they needed to. Their government was tremendously expensive. Their army and their navy with its strategoi and drungariuses (generals and admirals) cost them a lot of money and so did their extravagant ambassadors. The church with its own mighty army of high officials and lesser functionaries was very expensive too.
But as long as the Byzantines were not only able to support emperor, army, navy, diplomats, and the church, but were willing to do so, the Byzantine Empire flourished and was great. It was only after they began to economize, when a lot of Byzantines decided they were spending too much on the army, that their troubles began.
At the head of the government was the emperor, and he was certainly the most absolute ruler there could possibly be. Even in the earliest days of the empire, he was chief of the Byzantine state, commander in chief of the army and navy, the only one who could make laws, and the head of the Byzantine courts. In other words, he was equivalent to the President, Congress, and the Supreme Court of the United States rolled into one.
When he became basileus, he was even more than that. The Great King was master and owner as well as sovereign, and his subjects became slaves. They had to humble themselves on the ground before him, and foreigners had to as well. Beside that, he was the head of the Byzantine church (now known as the Greek, or Orthodox Eastern, Church), and in this connection took on another title, isapostolos, which is Greek for “equal to the Apostles.”
But in spite of his great power, in many ways he was a democratic emperor who was elected or at least chosen by a process carefully set down by law. First he had to be named by either the senate or the army. Then he had to be approved by whichever of those two bodies that had not named him in the first place. Finally he had to be hailed by the people. (This was true even when the emperor seized power or when an emperor named his son co-emperor so that he would be sure to succeed him. He still had to be approved and hailed.) But once the emperor was elected, he was “the emperor chosen by God,” for the Byzantines firmly believed that God guided them in everything they did. From then on, it was not only treason but wicked and sinful to oppose the emperor. That is, unless you were successful. If you led a successful revolution, it meant that God had chosen you to take the old emperor’s place!
The empress—the Augusta, or basilissa, as she was also called—was almost equally important. To be sure, in the long history of the Byzantine Empire, only three women actually mounted the throne to rule in their own name, and only one of these amounted to anything. This was the wicked Irene who wanted to marry Charlemagne and who blinded her own son so she could stay in power. However, she did not call herself empress. She called herself emperor of the Romans just as if she had been a man.
But even though she rarely ruled, the empress was not shut up in a harem, and many empresses had great power and even greater influence.