1) The Eastern Roman ("Byzantine") Empire to the west of Arabia and the Persian Empire to the east had been ferociously beating each other up for a long time, Persians capturing Jerusalem for example in 618 and 632. So both were militarily exhausted.
2) The huge plagues that also weakened the forces that were thus unable to counteract the Arabs.
Therefore, Islam is really more like an opportunistic weed. It makes sense, once you think about it, to back-invent a "cause" for this unexpected military success, and why not a mythical "prophet" to "inspire" them?
Completely agree w/ opportunistic nature of Islam, etc...
Imo, Mo did exist, but his "prophethood" was a myth. To be precise, in Arabic "Rasul" means "messenger", not "prophet". So, in Arabic, Mohamad is known as "Rasul Allah" (messenger of Allah).
The other incentive was about economics or the acquisition of wealth - link in #70.
Good analogy. The Duchy of Lithuania came about when the Mongols had destroyed Kievan Rus and the Poles were not strong enough to take advantage.
It's like a civilizational virus -- destroying civilizations. Look at Yemen, Egypt, Persia -- centers of civilization once and now.... While India's cancerous part (pakistan) was removed, it still causes problems...