I started watching this drama because of the interesting plot of a princess turned warrior and I was very happy to find Kim So Hyun in the lead role. On Dal played a vital role in the story though I think it focused on Pyeonggang/Ga Jin more so I don't really get why they wrote at the beginning of very episode that it's a story based on general On Dal's life lol. :D
The change of the actors didn't really bug me that much and I think Na In Woo did a really amazing job and his chemistry with KSH was so good! They easily become one of my favourite couples with their selfless love for each other.
I was rooting for the secondary couple as well but later I really started to despise Go Geon a lot. Mo Yong truly deserved better and I'm glad that at least she got the ending she had.
But the overall ending! Gosh that's the main reason why I gave the drama a lower rating because at first I was going to give 10/10. But then the last four episodes came out… After the four year jump everything went downhill. The sweet Prince was acting so power hungry out of nowhere and treating his sister awfully without any proper explanation. :/ We never saw some of the secondary characters, who have just disappeared with a trace (the concubine Hyeon Bi, Ga Jin's adoptive father, the little girl Wol from Baekje, the woman who was in love with Chief Sa…). Go Geon got such a long and draggy dying scene ugh. On Dal's own death felt so rushed but the fact that he actually didn't die was even worse. I think that they should have just let him die instead of making such a forced clichéd romance ending tbh.
Overall a great drama with the worst ending possible. :')