This is what someone I know said about the game:

HoI4 is incredibly easy
It'll really shine in MP though
And with ahistory mods
I conquered the japanese mainland as new zealand 4 years into the game
They had all their troops fighting the soviet union in the depths of siberia with no manpower left
So I jsut went in with some marines
and they surrendered when i took tokyo because they had china as a puppet
I wish the UK had an unholy alliance option with Germany
To murder France, the USA and the SU
I must admit though, literally being Hitler is very amusing.
Its a fun game, but very little replayability.