In 1965, the CS declared war on Japan, and within three months created a police state on the island of Hokkaido. It was known as North Nippon. Throughout the following years, it was subjected to even harsher laws than the Chinese State had and was mostly used for military training.
The Japanese Republic had tried many times to go to war with North Nippon and the Chinese State, but was annihilated every time. After their second war, the Chinese stated that they wouldn't seize Japan again as long as they promised to never dispute the reality of North Nippon ever again.
During GWII, there were many attempts by the Confederation to nullify North Nippon, but it was able to hold back most of it's attacks. Throughout GWII, most citizens of the country over the age of eighteen were forced to fight. North Nippon had about 1.5 million soldiers on call by 1971.