Constantinople went through a number of attacks over its history, but the first siege is the one that is known best and referred to as the Siege of Constantinople. It occurred from 674-678 and was perpetrated by Arabs. This siege was a major conflict of a long lived Arab-Byzantine war. This was the first in many moves by the Muslim Arab empire towards expansion. Their ruler, Caliph Mu’awiya I, was the one that led this initial assault. Before this there had been a civil war inside the Muslim Arab empire that had halted aggressions between the empires, but Mu’awiya felt it was time to revive their previous efforts.
Very early their eyes were set on Constantinople as it was believed that by strangling that city they would quickly be able to gain ground. The assaults were methodically executed as they began to set up bases throughout Asia Minor in the years preceding the actual siege. Essentially they were successful in setting up a blockade that slowly began to put stress and pressure on Constantinople and its rulers.
During two years of the actual siege the Arabs were successful in attacking the fortifications of the city, slowly weakening it. Fortunately for the Byzantine Empire, a new weapon was developed, that when deployed with the approval of then ruler Constatine IV was able to destroy the Arab’s naval fleet. That weapon was none other than Greek Fire, which was a liquid that was able to remain lit when in contact with water. After the demoralization of the defeat of their navy, the army was soon after defeated by the Byzantine Army, essentially ending the siege.
However, this was not the end of the tensions between the Arab Empire and the Byzantine Empire. In fact, in the years that follow they met in the same way again. That occurred, however after a lengthy hiatus due to another Muslim civil war.
This battle was extremely critical for the survival of the Byzantine Empire. The Arabs were accurate in judging that if they were able to make Constantinople fall the remaining empire would likely fall as well. It was a city the held the rest of the provinces together. The fact that the Arabs lost gave the Byzantine empire increased prestige and notoriety. It was quickly known by many other empires what had occurred. Not only did Byzantines win, but they had unleashed a terrifying weapon never seen before.