At times, as in the conquest of Greece by the Romans, military history can seem like destiny. The Roman civilization developed and ruthlessly employed a superior fighting method to conquer a civilization whose military methodology, like its culture, had grown old. Rome conquered Greece, and then ruled the world for half a millenium. The rest, as they say, is history. In this way, military history is history, and the consistent superiority of one army, one general, or one method over another becomes the superiority of a nation or people over another.
By just the same principle – that military history is history – the vicissitudes of battles, the tricks of fate, can also become history. It is this, I think, that made the world Christian, or at least stopped it from becoming Muslim. After the rise of Islam, which, as discussed earlier, is a pointedly militaristic religion, Muslim armies conquered much of the civilized world, rapidly moving outward from Arabia to conquer eastward to the Indus, and westward through Egypt, across the southern Mediterranean coast, and up into Spain. The Muslim armies also moved northward, spreading with their religion into Turkish lands. In every direction, the seemingly liquid flow of the armies was stopped only by geographical obstacles: the Pyrenees, the Sahara, the Indus, the Himalayas, the Russian steppes (and the Mongol hordes).
In one direction alone did the Muslim armies not expand: northwesterly, through Constantinople. The city was ideally situated for defense, with only one side exposed to land, and surrounded on the other three by the waters connecting the Black Sea to the Mediterranean. Through Constantinople’s peninsula lay the only practical land route from the Middle East to Europe, and through the waters dominated by this peninsula, the easiest sea route. In Durant’s telling (and Wikipedia’s), though, geography alone did not save Constantinople from the Muslim armies. Technology, instead, was the deciding factor.
For Byzantium had Greek fire. In an age when fighting was decided by swords, spears, and anything else blunt or sharp you could hit your enemy with, the Byzantines were among the first to pioneer the use of incendiary devices. Greek fire, the composition of which is now unknown, was primarily used by the Byzantine navy. Shot from pressurized jets mounted on Byzantine ships, the fire was a deadly incendiary to the wooden navies of ages past. In many engagements over several centuries, the devastating effects of Greek fire allowed small and hastily improvised Byzantine fleets to destroy massive Muslim fleets. The Byzantines recognized their debt to their Greek fire, and as a consequence, kept the secrets of its composition closely guarded. They were so successful that it is to this practice that we owe our current ignorance of the nature of the incendiary.
Considering the success of the Muslim armies on every other front, and their seeming unstoppability, it staggers the mind to imagine how history might look if this tiny civilization jutting into the Sea of Marmara had not been the sole possessor of Greek fire. After Constantinople, the Muslim invaders would have faced little organized resistance in the chaotic and poorly-developed areas to the west. They would have run roughshod over all and sundry until reaching the Alps. To the south, Italy was not united and in little condition to resist. To the north, Germany was a mere collection of Gothic tribes, and to the northwest it seems doubtful that the weak Carolingian kings of France, absorbed in fighting off Northern invaders, would have provided much resistance.
It is amazing the tricks that history can play.
Edit: Carolingian kings, not Merovingians… I was off by hundreds of years in my description of France.