The original Kongo machinery combined coal firing with sprayed fuel oil, preserving an ability to operate on domestic coal at reduced efficiency. Conversion to oil-fired machinery helped the reconstructed ships maintain speed despite added displacement and protection. That improvement also deepened Japan's strategic dependence on imported petroleum because the country possessed coal but lacked sufficient domestic oil. The propulsion refit solved a shipboard problem while creating a larger national logistics problem.
Notable Point · 1:07:17-1:08:31
Kongo modernization traded coal security for oil performance
More efficient oil-fired machinery preserved Kongo-class speed while making Japan's capital ships more dependent on fuel the country did not possess domestically.