At first glance, we might want to compare the expansionist desires of radical Islam with the Roman or Persian Empires. But they're different. Here is why the Roman and Persian Empires succeeded, where the Islamic caliphate is destined to fail...

The Roman Empire (before the official adoption of Christianity) was a geopolitical force. They conquered, but not under the illusion of religious conversion.

Rather, the Romans (and Persians) allowed their conquered subjects to continue to worship their own gods, and to keep their own culture.

Rome merely required tribute and obedience to the secular ruler in Rome. Many in the lands that Rome conquered realized that the advantages of living under the Roman eagle surpassed the disadvantages. After all, they got to keep their religion, AND they benefitted from Roman infrastructure, law, protection, etc.

Radical Islam, however, seeks to conquer in the name of its religion. When a land is conquered by radical Islam, the conquered people's gods, and indeed, culture, are eliminated (for the most part), and Sharia Law is forcibly enacted. No longer is their secular and religious. There's ONLY religious, and it's the religion of Islam, the conquerors.

As the world modernizes, progresses, and becomes more learned, religion (especially absolute religion, practiced by radical sects of Islam) falls by the wayside, as reason, logic, and science, dictate more and more of humanity's motivations.

What people are going to want to accept Sharia Law? It's the law of a thousand years ago. There is no realistic enlightenment. The lines with which to color in between are narrow, and there is NO coloring outside those lines. In other words, mankind's ability to think independently, create, and innovate is severely limited by an oppressive, overbearing, rigid system of law which is couched in the conquering people's "religion".

No nation seeking to evolve is going to want that. The reason why western imperialism has been quantitatively more successful than Islamic imperialism, is because the West allows its subjugated nations to keep their culture. Islam doesn't. That's the difference in a nutshell.

Islam doesn't stand a chance in the future.