Amongst the newly added nations are two long-awaited heavy hitters in the form of the British Empire and the US.
Also joining in the fun/ terrible worldwide devastation are Australia, Union of South Africa, New Zealand, Dominion of Newfoundland, Portuguese Republic, Netherlands, and the Kingdom of Spain.
The update also adds "gas attacks, naval and coaling stations, unrestricted sub warfare, social welfare programs and propaganda, shore bombardment and many AI improvements". And a bunch of less glamorous fixes and technical tweaks, of course.
You can check the full list of additions out. Developers Muzzy Lane Software also point out that the new update will break any saved games you currently have. Such is the price of Early Access.