ABSTRACT
One of the reasons why empires rarely survive crises of succession or internal wars is their cultural and ethnic heterogeneity. If an empire never develops into a culturally and ethnically homogeneous polity, then any one of these crises could prove to be very fateful, or even its last. The ethnic and cultural heterogeneity of the Grand Duchy is obvious, and acknowledged by all researchers of the Grand Duchy. From the sixteenth century, the ethnic boundary between Balts and Slavs no longer coincided with the religious boundary between Orthodox and Catholic believers. Catholicism spread among Orthodox believers as well, intensive migration occurred from Poland (especially to Podlasie), and Polonisation started in ethnic Lithuania, primarily among the nobility. Classic examples of empires in which a politically dominant ethno-cultural group constituted a small minority were Achaemenid Persia, and the Mongol and British empires.
