Len Lease is Roosevelt's baby. It is one of the greatest foreign policy decisions ever made, and he made it.

The isolationists knew this was their final battle. If they didn't win this, it would mean that America was no longer neutral.

In December of 1940, British Prime Minister Winston Churchill wrote to President Franklin Delano Roosevelt with chilling news.

The war with Germany had drained the British Treasury.

London would soon be unable to pay for the supplies and weapons it was buying from the United States.

Knowing he had to act, President Roosevelt mustered political support at home

for military supplies to friendly democracies in Europe.

The resulting LEN-Lease Act became one of the most contentious and consequential decisions

in U.S. history. Why was the Lenn-Lease Act so controversial? And how might the work have gone

differently without it? From the Council on Foreign Relations, welcome to the president's inbox. I'm Jim Lindsay.

Joining me today is historian Lynn Olson, author of Those Angry Days, Roosevelt, Lindberg,

in America's fight over World War II. Lynn, thank you very much for joining me.

Well, thank you very much for having me.

In recognition of the 250th anniversary of American Independence, Lynn,

we are devoting one episode of the President's inbox every month

to a pivotal moment in the history of U.S. foreign policy.

The enactment of the Len Lease Act on March 11, 1941, certainly qualifies on that score.

A recent survey I did with members of the Society for Historians of American Foreign Relations

ranked the Len Lease Act as the fifth best decision in U.S. foreign policy history.

Yet I think you can only understand the battle over the Lenn Lease Act

by knowing a little bit about the history of the decade leading up to World War I.

So could you help us, Lynn, by sort of explaining what sort of the nature of the debate over America's role in the world in the 1930s?

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