When should Germany have surrendered?

[Periander]

True, but don't forget circumstances changed between the armistice and the peace treaty being signed. The Imperial Navy fearing that the diplomats were selling them down the river (which they weren't) scuttled the Fleet at Scapa.

Scuttling is an act of war - IIRC in that by scuttling you are denying a victor his rightful spoils and all that. Anyway whatever the reason, it is an act of war by common usage and law.

By committing an Act of War during an armistice the Germans were knocked on to the back foot politically and essentially stuffed themselves.

Again though it should be noted that as in WW2, Ike in particular was responsible for much of the post war misery that could have been avoided by earlier cooperation with the defeated Germans it was President Wilson who insisted that essentiall the German state should be punsihed so hard it would take a generation to get back on its feet.

A very, very short sighted policy.