Iraqi and U.S. troops have been fighting militants in Diyala province, which stretches north and east of the capital and borders Iran.

CNN: Bombings kill at least 60 in Iraq

The head of oil research at Barclays Capital, Paul Horsnell, described the current situation as potentially worse for oil than the Iran crisis of 1979.

FORBES: The Libyan Crisis: Where Are Oil Prices Going?

In the new Discovery Channel documentary, Koppel travels to the border of Iran's border with Iraq, the ancient capital of Isfahan, the holy city of Qom and the Persian Gulf.

NPR: Koppel: Inside Iran, 'The Most Dangerous Nation'