By George Friedman For centuries, the dilemma facing Iran (and before it, Persia) has been guaranteeing national survival and autonomy in the face of stronger regional powers like Ottoman Turkey and the Russian Empire. Though always weaker than these larger empires, Iran survived for three reasons: geography, resources and diplomacy. Iran's size and mountainous terrain made military forays into the country difficult and dangerous. Iran also was able to field sufficient force to deter attacks while permitting occasional assertions of power. At the same time, Tehran engaged in clever diplomatic efforts, playing threatening powers off each other. The intrusion of European imperial powers into the region compounded Iran's difficulties in the 19th century, along with the lodging of British power to Iran's west in Iraq and the Arabian Peninsula following the end of World War I. This coincided with a transformation of the global economy to an oil-based system.