"Ring of Red" is set in an alternate history 1960s where the Allies ended World War II by invading Japan in the costly Operation Downfall rather than the use of the atomic bomb. With the Cold War looming over the horizon, Hokkaidō is ceded to the Soviet Union, and the remaining portions Japan are partitioned into Communist Republic of North Japan and democratic South Japan. North Japan was supported by the Soviet Union and the People's Republic of China, while the United States and other democratic countries supported the South, and Germany makes engineering contributions to both sides.