This release includes the Northern Expedition Scenario, with playable KMT, Zhili Clique, Nanjing Clique, Fengtian Clique, and German Empire factions.
Install the mod by extracting the archive in your Darkest Hour/mods folder.
You can also download the mod which this scenario was based on, Kaiserreich: Legacy of the Weltkrieg, here - Moddb.com