The Shōwa period (1926–1989) witnessed dramatic shifts in Japan’s postal history, shaped by militarism, war, defeat, and postwar recovery. In the 1930s–1940s, Japan’s postal system expanded aggressively across occupied territories in Manchuria, China, Southeast Asia, and the Pacific, issuing military and civilian occupation stamps to assert control. During World War II, field post offices (gunji yūbin) served troops across Asia, often with locally printed or overprinted issues. After Japan’s defeat in 1945, the Allied Occupation (1945–1952) reorganized the postal system under strict supervision, introducing censorship and new stamp designs. In the postwar economic boom, Japan’s postal services modernized rapidly, embracing automation, airmail expansion, and international cooperation. The Japan Post Savings system also played a key role in funding national reconstruction. Under Emperor Shōwa, Japan’s postal network evolved from imperial infrastructure to a globalized, civilian-centered institution.