There are are probably no event or sequence of events that could be considered pivotal. However, one of them has to be the sieges of Constantinople in the early 8th Century. The Byzantine empire was at a point of shrinking due to incessant attacks and invasions by Islamic forces. In 610 the Islamic Prophet Muhammad began receiving what Muslims consider to be divine revelations. These concepts drew a large number of people to accept these as a way of life and by the time of Muhammad's death in 632, there were a considerable number of influential leaders who had fully embraced Islam. These men were spurred to begin a program of conquest to bring Islam to the infidels and to unite the world under one religion.

While many areas embraced Islam, it wasn't the case everywhere these armies went and one place was Christian Byzantium. Especially in those days, religion was power and a main way to control the masses. Islam eventually took over much of North Africa and into the Iberian peninsula in a remarkably short time. However, the Byzantine empire, such as it was, became a major block.

Byzantium had several major factors going for it. One was the Tarsus mountains in eastern Anatolia. It was a rugged line with few passes and was easily defended. Another was that Constantinople itself was heavily fortified and nigh impregnable at the time. The Byzantine fleet also had a terrible weapon in what is known as Greek Fire. This concoction is very much like napalm and once it hits you, cannot be extinguished, even by immersion in water.

However, the caliphs were determined and for decades were able to eventually get past the mountains and up to the eastern side of the Dardanelles, where they set up siege weapons and gathered their troops. Not surprisingly, they were stymied in most of their attempts to land troops and supplies by sea near Constantinople by Greek Fire, and eventually, even their biggest and most successful campaigns were forced back by Anatolian winters, which can be quite harsh.

As we all know Constantinople was finally to succumb in the 15th Century, but it did not happen earlier. So why is the last major attempt in 717/8 considered pivotal? Had the Muslims succeeded, they would have had an open way into the rest of the Balkans and eventually into Europe. This would have driven Christianity to near extinction and made the world a very different place than what it is now. 

The author had done an outstanding job of telling not only the tale of all the events leading up to the pivotal siege, but also of the siege itself. He also provides us with a look at how it affected the world order and what could have been if it had succeeded. The book includes not only great maps, but some super period art work and photos of many of the areas as they look today. It is one into which one can easily become immersed and tells a story of which few are truly aware. It is a book that I can most highly recommend to history buffs.