Three 500,000-ton super-ships appear in Japan

How would three 500,000-ton super-ships appearing in Tokyo Harbor in 1937 change World War II?

They would trigger a major Anglo-American naval response, but Japan’s oil shortage and the ships’ extraordinary operating demands would sharply limit their usefulness.

Japan’s first problem would be finding enough oil to move three ships of such extraordinary scale and speed. Their appearance in 1937 would end Anglo-American willingness to remain within existing treaty assumptions and push new battleships toward 18-inch or still larger guns. Britain could also mass-produce T-class submarines, accelerate Torpex, and seek enough concentrated torpedo damage to defeat the giants without matching them hull for hull. Even a grounded or bottomed super-ship could remain an immense fixed battery in shallow water, making bases and island campaigns harder to attack. The four years before the Pacific War would therefore become an arms race between Japan’s operational limits and Allied counters to a visible 1.5-million-ton threat.