If you are looking for help with a specific part of the game, I can:

Hearts of Iron III (HoI3) is often cited as the most "hardcore" entry in the series. Unlike its successors, which streamlined several mechanics, HoI3 features a highly granular system. Players must manually organize their military hierarchy, from individual divisions up to theater commands, ensuring that every unit is within the radio range of its superior officer to receive combat bonuses. This level of detail offers a rigorous simulation of 20th-century chain-of-command challenges. Global Scope and Historical Sandbox

Give you a for a specific country like Germany or the USSR.

: Added deeper covert operations to sabotage enemies or support coups.