What are some ultranationalistic empires that lost their culture and religon through their expansion...like coverting
One early Egyptian pharoah (emperor):
http://www.google.com/search?q=amenhotep+iv+akhenaten&ie=utf-8&oe=utf-8&aq=t&client=firefox-a&rlz=1R1GGGL_en___US357
The Roman Empire
Alexander the Great's empire
Genghis Khan's conquered territories
As each got larger and larger, the central government had to depend more and more on the conquered governments to "mind the store." Needless to say, that can't go on very long before collapse.