The military source said the order was issued in response to tensions in the East China Sea over the Senkaku Islands and meant that all military branches were preparing for war.

A similar order was last issued in 1979, immediately before China’s military intervention with Vietnam following the country’s invasion into Cambodia.

After the latest order was issued, the PLA shifted fighters from inland areas to coastal areas such as Shanghai and made other moves, Japanese and U.S. government sources said.