CORE is a mod aimed at recreating the period 1936-1952 in the most historically accurate manner possible while still allowing the player as much freedom of choice and direction as is plausible.
What that means: CORE goes into a lot more detail than the vanilla game in terms of technologies, units and events. Nations have techs representing their relative level of development industrially and technologically, tech representing the prevailing military mindset, and so on. There is a representation of both nations producing domestically high technology items like planes and tanks, while also representing nations who had poorly developed or no industry in these areas. The land, sea and air units have been totally reworked to better fit the actually used units of the era into the model given in HoI2, including such details as differentiation between large and small pattern divisions, first and second class infantry divisions, a substantially expanded and nuanced naval tree and a very well developed air tree incorporating not just development of the aircraft themselves but also the underlying industrial base. Doctrines have also been comprehensively reworked to reflect the changes and again to better fit how the team sees the evolution of doctrine in the period. The land tree, for example, comprises many incremental developments in a wide variety of fairly specialised areas of focus, while the aerial tree charts the development of national air forces from rudimentary air force, incorporating operations focus, into the jet age. The industrial tree seperately charts the nations recovery from the Great Depression, the development over time of heavy and light industry, and the evolution of industrial science, while the secret weapons tree covers the full development history of both nuclear weapons programmes and rocket and jet programmes, plus a few other surprises. The ever-expanding package of events represents major events both within and between nations of the time.
CORE offers a greatly expanded experience, and IMO is the most in-depth representation of the period. There's a propaganda minister around here somewhere who could expand further.
