After masterminding the attacks at Pearl Harbor, Japanese Adm. Isoroku Yamamoto knew that his country's dominance of the Pacific Ocean would not last against the U.S.'s industrial might.
He began forming plans for a weapon that could terrify the U.S., especially eastern cities like New York and Washington D.C. He thought a campaign of vicious attacks on the east and west coasts would convince the U.S. to quickly sue for peace.
U.S. Carriers on "Murderer's Row" at Ulithi Atoll. Photo: Wikipedia
To maximize the chance that the planes would reach their targets, the Japanese admiralty ordered the planes be painted silver with U.S. markings. Though the pilots protested, the illegally camouflaged planes were placed in the subs and sent to sea.
Luckily, Japan surrendered while the subs were staging for the attack. Both subs were captured by the U.S. Navy. American officers studied the ships but then sank them before Soviet officers could ask to see them. There was concern that the Soviet Union would develop its own version if it saw the I-400.