 In his book "", Dr. Ian Bremmer, president of the Eurasia Group, argues that a superpower is "a country that can exert enough military, political, and economic power to persuade nations in every region of the world to take important actions they would not otherwise take".Apart from its common denotation of the foremost post-WWII states, the term "superpower" has colloquially been applied by some authors retrospectively to describe various preeminent ancient great empires or medieval great powers, in works such as Channel 5 (UK)'s documentary "" or the reference in "The New Cambridge Medieval History" to "the other superpower, Sasanian Persia".The 1956 Suez Crisis suggested that Britain, financially weakened by two world wars, could not then pursue its foreign policy objectives on an equal footing with the new superpowers without sacrificing convertibility of its reserve currency as a central goal of policy.