Much of the Japanese planning for Pearl Harbour centered around the use of torpedoes in shallow water and able to skim over the anti-torpedo netting. The British attack on Taranto showed that it could be done and this was a final lynch-pin in the Japanese attack plan. But...what if the attack on Taranto never happened or was a complete failure. How would that affect the Japanese plans. Later Pearl? No attack on the US or a China-first policy?