What the Japanese did to prepare for invasion?

In preparation for a potential invasion during World War II, Japan fortified its home islands and established a defensive strategy that included constructing extensive coastal defenses, military bases, and airfields. The Japanese military also stockpiled resources and munitions to sustain prolonged conflict. Additionally, they mobilized civilian and military personnel, creating a network of underground facilities to support resistance efforts against invading forces. These preparations aimed to deter invasion and ensure a robust defense against Allied forces.