Sarah Paine

So it's looking like it might be okay for the British for a while, except Donitz thinks something's up.

And so they add a fourth rotor to the Enigma machine.

And so the British are then blind again for most of 1942 until they can capture a four-rotor Enigma machine, all the rotors plus the code books.

It takes a while.

So they're in a world of hurt.

The United States enters the war, which you think would be good for Britain, except it produces Hitler's second happy time.

Why?

Because Admiral King, like his Royal Navy predecessors in the previous war, doesn't think convoying is the manly thing for naval officers to be up to.

So he's not for convoying.

Also, Americans don't turn off the lights.

And therefore, as merchant ships are going up the east coast of the United States, the lighting is just highlighting their silhouettes, making them much easier to sync.

And oh, by the way, in those days, Louisiana, Texas oil, which is supplying the east coast where a lot of American industry is, is coming up by ships on the eastern seaboard, and particularly by Cape Hatteras shoals, which are like 30 miles wide, become a total kill zone.

So Admiral...

King rethinks it after losing more than a million tons of tonnage in the first three months of 1942 and goes, oh, gee whiz, maybe we should do convoys.

Yes.

And the United States does interlocking convoy system by May of 1942.

But then Dunitz just starts hunting things a little further south in the Caribbean.

So the Brits get their four-rotor Enigma machine, and they're able to decode things again.

But there's another problem.

The British think that there's something up with their admiralty codes in August of 1942, but they don't change them out until June of 1943.