Put simply, CFCS is a total rework of Blitzkrieg. It is at it's heart a realism mod, but there are of course some compromises for gameplay reasons. It covers the traditional Second World War period, that is 1939 to 1945, the same as the original game. It does expand this to cover the Pacific, China-India-Burma and Far Eastern theatres, as well as looking at all theatres and campaigns in more detail. There are also addons that cover the Spanish Civil War (1936-1939) and Korean War (1950-1953), as well as "What-if" 1945 chapters covering a continued war between the Allies, Germany and the USSR with interest new weapons and equipment, as well as a theoretical conflict between the West and the USSR. For map makers, it also includes a substantial toolkit of new units, objects, buildings, and so forth to create almost any conceivable scenario from the 2nd World War.
One of the best mods out there.
Good game, lots of work went into it, you can tell
A sweeping and total overhaul of core mechanics, campaigns and units. Simply reading a review doesn't do it justice.
A lot of work and time was put into it, if you're wondering about the negative reviews, here's an answer : Warthunder players - a demographic which balks at the concept of historical accuracy.