Much of the Middle East is now Islamic. Muslim warriors conquered it centuries ago, and Sharia law has been slowly eliminating the last remnants of non-Muslims ever since. Now some orthodox Muslims are working to conquer Europe.
But why is Islam so different from other empires that have come and gone through history?
The Mongols conquered the largest landmass ever controlled under one government, and if Genghis Khan hadn't died when he did, his warriors may well have conquered Europe.
But nobody is worried about the Mongols now. Why?
Because they didn't write a book and they didn't start a religion. There are no faithful followers of Genghis Khan still working to fulfill his vision of world conquest.
We cannot say the same about Muhammad.