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Hello, I'm Justin Webb.

Welcome to the documentary from the BBC World Service.

In this edition, I'm exploring the evolution of US foreign policy

through five presidents and five key doctrines.

My guests are I will look at how America's approach to the world has constantly changed over time,

from the Monroe Doctrine in the 19th century to the post-9-11 strategies of the Bush doctrine in the early 2000s.

This may help us answer a really big question.

How radical is the way Donald Trump deals with the world?

Is he really an outlier in US history?

Or do his actions merely reflect the changing patterns of American power?

I'll be asking a range of experts

how America's approach to the world has changed over time.

And we call this program US foreign policy in five doctrines

in homage, of course, to the great granddaddy of them all,

the Monroe Doctrine of 1823.

It's an outlook that looks like it's back in fashion, too.

Jay Sexton is Professor in History and Director of the Kinder Institute on Constitutional

Democracy at the University of Missouri, and is author of The Monroe Doctrine, Empire and Nation

in 19th century America. Jay, kick us off, if you would, with James Monroe and his

times. Who was he? What was happening when he was around? He's the last founding father president.

He has the connection to the revolution, actually served in the revolution, was with

...