SGS Operation Downfall

SGS Operation Downfall is a strategy game about a hypothetical Allied invasion of Japan in 1945 and 1946, based on Operation Downfall, the planned invasion that would have followed if the atomic bombs had not been ready in time. You play through the landings and amphibious assault on the Japanese home islands, including Operation Olympic on Kyūshū and Operation Coronet on the Kantō Plain near Tokyo. The scenarios also cover possible Soviet intervention against Hokkaido, Japanese domestic politics, the Emperor and the risk of his capture.

Scale and scenarios

Land units operate at division level and air units at wing level. Naval forces are abstracted, while weapons such as kamikaze aircraft and midget submarines appear through events or combat cards. Each region covers about 100 square miles, and each turn represents one week. Scenarios range from 10 to 27 turns and offer different starting options, including troop levels, replacements, air support, initial positions and airborne operations.

The opposing forces

Japan has few mobile troops, armor, artillery and aircraft that can match Allied planes, but its fixed defenses are strong and difficult to break. Terrain, population loyalty and dedication, cards and events shape its fierce resistance. Allied forces have strong equipment, air power and naval gunfire support, but must meet tight timelines and objectives while securing harbors for supplies and airbases for redeploying tactical air support. The season and poor weather prospects add to their constraints, which are reflected in their cards.

Political pressures

The game represents tensions between the US Navy and Army over the plan and the weapons to use, as well as divisions within Japanese leadership between the Peace Faction and those prepared to fight on. The invasion’s projected casualties were extremely high, with estimates reaching into the millions for Allied forces depending on Japanese civilian resistance, and the prospect also carried major political consequences in the United States.