This alternative timeline starts at the end of the Great War, in October 1918. The German Imperial Admiralty Staff was arguing about attacking the British Grand Fleet for a decisive sea battle which in reality led to the Sailor's revolt in Kiel and later on to the German Revolution where Emperor Wilhelm II. resigned and the Weimar Republic was established.
In this story, the German admiralty decided not to attack the British Fleet and accepted the loss of the German Empire. You will read what happened to certain countries in their own article.