FDR gets advance warning of Pearl harbor

[Blue Max]

Here's a very simple question:

Suppose that on November 24th, the USA, after breaking Japanese Codes (I believe that had done so before Pearl Harbor) learns that Pearl Harbor is going be hit on December 7th?

Granted that FDR wants a war, but this puts him in a very awkward situation. On one hand, if knows of the attack and it confident that it will happen (as I suggest), failing to respond to it before it happened could well result in his impeachment. On the other hand, going public with the knowledge would almost certainly scare off the IJN and the USA would be unenthusiastic about the war without Pearl Harbor.

What would likely happen?

[CalBear]

He calls the Japanese on their plan, once some sort of cover story is created to protect the information source.

FDR didn't want war with the Japanese, he WANTED war with the Reich, seeing them as a basic evil that had to be stopped. A war with Japan would simply be a distraction drawing American attention from Europe.

FDR was right. If Hitler hadn't been a complete nutjob he would have wished Toyko good luck and concentrated on the USSR. Without the German DoW, the Congress would almost certainly have screamed for Japanese blood and ignored the Reich.

[Tony Williams]

I suspect that he would take precautions to strengthen the defences, but not make any public announcements.

If the Japanese realised that they had been rumbled, they'd abort the PH raid, but I suspect they would still attack the Philippines, which on its own would be likely to trigger war.

[Riain]

I think it is a bizzare conspiricy theory that FDR wanted war with the Japanese and let PH happen in spite of his pre-knowlege. In it's even more bizzare forms FDR is a great visionary who organises the carriers to be absent on the day of the attack so the battleships can be removed in favour of carriers as the future of war. The whole idea is strange, becuase even if he did want war, having US forces mount a huge ambush on the Japanese would get the US into the war without the huge setback of PH.

That's what I think would happen, an ambush set up at the highest levels, and preplanned perations launched on receipt of a codeword.

[wkwillis]

You know, the Japanese fleet didn't really have any reason to be wandering around the North Pacific way out there unless they were going to hit Pearl Harbor, or maybe Seattle...

[bard32]

Originally Posted by Blue Max

Here's a very simple question:

Suppose that on November 24th, the USA, after breaking Japanese Codes (I believe that had done so before Pearl Harbor) learns that Pearl Harbor is going be hit on December 7th?

Granted that FDR wants a war, but this puts him in a very awkward situation. On one hand, if knows of the attack and it confident that it will happen (as I suggest), failing to respond to it before it happened could well result in his impeachment. On the other hand, going public with the knowledge would almost certainly scare off the IJN and the USA would be unenthusiastic about the war without Pearl Harbor.

What would likely happen?

Well, FDR did get a warning on December 6, 1941, IOTL. If he got advanced warning two days before the carriers sailed, it might not have made any difference. He knows sooner than he did IOTL. What difference would it make? According to a 1972 article in LIFE magazine, if the ships of the Pacific Fleet were at sea, and encountered the Japanese carriers and their escorts, they would have been beyond recovery. This is according to a book called The Dictionary of Misinformation.

[bard32]

Originally Posted by CalBear

He calls the Japanese on their plan, once some sort of cover story is created to protect the information source.

FDR didn't want war with the Japanese, he WANTED war with the Reich, seeing them as a basic evil that had to be stopped. A war with Japan would simply be a distraction drawing American attention from Europe.

FDR was right. If Hitler hadn't been a complete nutjob he would have wished Toyko good luck and concentrated on the USSR. Without the German DoW, the Congress would almost certainly have screamed for Japanese blood and ignored the Reich.

We broke their diplomatic code by November 1941. So we knew the Japanese were going to break off diplomatic relations with us. They'd sent a fourteen-point diplomatic telegram to their embassy in Washington. The last part didn't arrive until just before the attack on Pearl Harbor. About 24 hours
before the attack on Pearl Harbor, I think. I'm not sure. So DON'T QUOTE ME
ON THIS. Anyway, FDR wanted to avoid war at the 11th hour. He was going to send another letter to Hirohito. Would you like to know why we were able to decode it and they couldn't? They didn't have a competent cryptographer.
The Americans joked that they should have had them decode it for them. FDR wanted a war with Germany and Italy. However, he didn't want to declare war on Germany. So Hitler saved him the trouble. When Churchill and Roosevelt signed the Atlantic Charter in August 1941, Roosevelt promised Churchill that Germany, not Japan, would come first.