The Second Schleswig War is an interesting footnote in 19th century history, and it's good they made a series around it to highlight how it was experienced by different people. And for the most part it is done well; the emotionally passionate but not really all there in the head Danish Prime Minister and his friend the opera actress are both excellently portrayed. The scheming Bismarck, the internal problems facing the Prussian and Danish armies and so on are all well done. Now on a personal level I would've liked the show to be just that; the decision making of the people involved, their ideals, sympathies, mistakes and tragedies. That is what makes for good historical drama. However, such scenes are quite rare.
The problem with 1864 is that it doesn't focus too much on that, and rather wastes its time with a love-triangle between 2 brothers and their girlfriend. And on top of that an unneeded segway into some unlikeable girl and a senile grandpa in modern times reflecting on what happened in 1864. And that's a shame because there is a lot of rich history under the surface.