This will be a quick review as I'm struggling. I want really to like this show because it has a stellar cast. However, it is very very dense and needs your full attention. Even though my grasp of modern Korean history is so-so, it still didn't help me in this show.

The first episode just drops you in and you don't really know what's happening and who everyone is. However, I can see the bones of a good story unfolding. One does need patience. I will update the review again at the end.

Update: It was still very dense at the end. Too many side characters and trying to keep track of each character's dynamic agenda and ever-changing allegiances was tiring.. It felt like the show's writers tried to keep it true to history (interspersed with historical segments), yet it was not meant to be historical (as the beginning caveat clearly states).