The Historical Plausibility Project is a mod for Hearts of Iron 3 and its expansions with the goal of helping the game reach its full potential as a half-historical / half-sandbox game. The mod features a vastly improved AI, historical OOBs for every nation, complex internal politics, a reworked leadership system, the Soviet invasion of Poland, HOI2-style doctrines, capital ship modernizations, over 6,000 unique unit pictures, and much more. The HPP is the result of the efforts of the HPP team's five members of Slan, TheBromgrev, TZoli, SSmith, and Nephandus from the ParadoxPlaza forum, and its main forum is its official ParadoxPlaza forum, which Paradox requires proof of game ownership to enter. The HPP's forum contains the mod's FAQ, Submod downloads, country guides, and small hotfixes. In addition, part of the mod's previous work to the East Asia part of the map is now in the Their Finest Hour base game for everyone to enjoy.
Some screenshots showing an advanced game as the People's Republic of China, an event related to Japan, and the naval limitation treaties.