This is the Memory Palace. I'm Nate DeMaio. It had looked like it would be safe, until the

boats started blowing up. German warships and air assaults had wreaked havoc in the North Atlantic

for nearly four years. And the U-boats, the submarines, made every crossing since the war broke out

in the fall of 39, a deadly game of chance.

More than 2,500 ships had sunk.

Navy, civilian.

More than 5,000 sailors and seamen, cooks, radio operators, passengers had been killed in open combat or by torpedoes,

slipping up through the depths while they slept.

But by the spring of 1943, it looked like the Allies had taken back control.

American shipyards had been launching vessel after vessel at astounding speeds,

new naval escorts for civilian ships, with the Royal Canadian Air Force keeping watch from above.

The British had put their best scientific minds on the task of freeing the Atlantic, breaking codes in Bletchley Park, developing radar that could find

the U-boats in the dark of the deep blue sea. But after a quiet summer, September was aflame.

Two dozen ships sent to the bottom of the Atlantic. Hundreds of people dead, drowned, blown up in their bunks.

And so that November, there was nothing to suggest it would be easy sneaking the president

across the ocean.

But Roosevelt was needed in Tehran.

The future of the war needed to be decided.

And no amount of encoded cables or envoys secreted across borders in the dead of night

could bring about a decision about the final assault.

Roosevelt, Churchill, Stalin, the three powers in one room.

It was the only way.

...