Joseph Grew and Pearl Harbor warning

Jan. 27 1941 - Joseph Grew warns of Japanese plan to attack Pearl Harbor. ONI (Office of Naval Intelligence) places "no credence" in Grew's rumors

Joseph Clark Grew was the Ambassador to Japan beginning in 1932.

http://en.wikipedia.org/wiki/Joseph_Grew

Anyone read how he got this idea and even sent it to his superiors? Thanx for any info!

 

Here is a link to the entire "memo", and Grew himself dismissed it:

http://www.mtholyoke.edu/acad/intrel/WorldWar2/grew3.htm

 

One reason I can see right off the bat for both Grew and the ONI dismissing this plan is that the USN Pacific Fleet was still based in CA. at the time, and wasn't relocated to Pearl until about 3 1/2 months after the memo.

On 7 May 1940, the U.S. fleet moved its headquarters from San Pedro, California, to Pearl Harbor. The move was undertaken with great reluctance by Admiral James O. Richardson, Commander in Chief, U.S. Fleet. Richardson and most Navy officials who opposed the move thought a fleet anchored in Pearl Harbor would be unnecessarily exposed to Japanese naval strength. President Roosevelt, however, considered the move as a necessary countermeasure to growing Japanese bellicosity.

From:

http://www.history.navy.mil/books/comint/ComInt-4.html

I personally feel that FDR felt that the Japanese would be inclined to strike south at the Philippines and the oil in the NEI area first. This move would put the fleet 3000 miles closer to the area, and reduce the time necessary for it to react to Japanese aggression in that area.