Japan conquered lands rich in oil and food, but Allied submarines sank the ships that carried them, so shortages grew.
Overextension means holding more land than your forces can defend and supply. Japan's conquests had oil, metal ore and food. But these had to travel by ship to Japan's factories, fleets and armies. Defending so many distant islands spread Japan's forces thin.
Allied submarines and planes attacked Japanese cargo ships and oil tankers. Sinking a tanker meant the navy got no fuel, even though Japan still held the oil field. Captured Allied bases made Japan's routes even harder to protect.
Fuel shortages cut training and operations. With less fuel, the navy could protect fewer ships. So more ships were sunk, and shortages got worse. Holding land did not guarantee that its supplies could reach Japan.
- Overextension
- Holding more land than you can defend and supply.
- Allied submarines
- Sank Japanese cargo ships and tankers.
- Vicious circle
- Less fuel, weaker defence, more ships lost.
Worked example: Follow the oil to the navy
Japan controls an oil field, but its fleet is far away.
- The oil must be loaded onto a tanker and shipped to the fleet.
- If a submarine sinks the tanker, the fleet gets nothing.
- With less fuel, the navy can protect fewer tankers, so shortages grow.
Watch out for this
Once Japan conquered oil-rich lands, it could not run short of oil.
Owning oil fields was not enough. The oil had to reach the fleet, and Allied attacks sank the tankers.
Check your understanding
Why did Japan run short of oil even after conquering oil fields?
- Allied submarines and planes sank the tankers carrying it.
- The oil fields were all destroyed in 1942.
- Japan chose to sell all its oil abroad.