The edo period lasts from the early 16 hundred til 18 68. The country is nominally run by something called a show gun, translated often as military dictator. During this time period, Japan split up into about roughly 200 separate little areas. Each one of these areas has its local lord, and they raise their own taxes. They owe allegiance to the central government, but have broad ranges of powers.
The Asia-Pacific War of 1937-1945 has deep roots. It also involves a Japanese society that's been called one of the most distinctive on Earth. If there were a Japanese version of Captain America, this would be his origin story.