The European Union is now a vast political and economic union of 28 member countries and, with more than 500 million people, its combined population is the third largest in the world after China and India.

But the European Union did not begin as a large political project – rather as a series of small steps in an American effort to promote postwar security, according to Mark Blyth, professor of international economics at Brown University.

As politicians in Britain struggle with the details of their country’s divorce from the European Union, Gillian Tett, U.S. managing editor of the Financial Times, and Blyth discuss the forces uniting Europe and the many issues threatening to tear it apart.