I'm not a big fan of nationalist or 1920s-1930s dramas. Also I only started watching for Ou Lao and Seven (2 actors I like in all of their works).

And I haven't regretted it!

I never do great analysis or very detailed commentary, so I'll keep it simple.
It is a fresco of thrilling adventure, well conducted, coherent, with a formidable cast.

1/ the cast:
I have already mentioned the 2 leads who bring this adventure to life with their usual talent. I just regret that their romance is so occasional on the screen. Their chemistry is obvious and OTPs are far too rare.
The secondary characters are well developed, with their objectives, their complexity, their paradoxes.

2/ The story:
I don't know enough about the history of China to judge the authenticity of the context, but the whole seems realistic.
Of course, the viewer is entitled to the refrain "everything for the people, priority to the nation, duty above all" but there is no escaping it in Chinese dramas and it is consistent with the context.
The narration is fast, the clues are given finely during the storyline. In short, the screenwriter and the director did an excellent job.
The action scenes are plentiful and extremely well done.

3/ OSTs:
There too, carefully chosen and adapted to the context, despite a few bugs (waltz tune when the dancers are visibly dancing to another rhythm, for example). I appreciated the opening and ending credits, lyrical, adapted to this great fresco of adventure.

I will definitely rewatch this drama (which is quite rare, for me) because I was glued to my screen for 3 days/nights, which gives the measure of its quality.

So, if you have a few days avalaible (because you're going to be hooked), don't miss this jewel, which won't disappoint you!