It is one of the strategy games focusing on World War Two made by Paradox Interactive. The requirement to take London means that you not only have to survive, but also win.
The requirement to free most of the African continent from the imperialist yoke means that you’ll be facing down the Allies with no support from the Axis or Comintern. Hearts of Iron IV is the fourth game in the Hearts of Iron franchise. An achievement rated insane on the Hearts of Iron IV wiki.