[Gator101]

That one of the reasons that the conspiracy theorists give as the reason the Japanese kept mum about their involvement and didn't pick up the German crew.

I think it's a bit far fetched myself. I don't think they would want to risk alerting the Allies about impending war so soon before Dec 7th.

[Tallguy]

There's probably another basic limitation to the Japanese/German cooperation theory: communications. Not likely that German & Japanese fleet units had the capability to communicate securely via radio. Different codes & encryption gear.