To my understanding, Kingdom mixes around historic facts and fictional storytelling in its exploration of Xin's struggles as a number of major characters are based on real-life historical Chinese figures. I am not well-versed enough in Chinese history to understand how much of what is depicted in the series is historically accurate. But in regards to the characters seen throughout the series, they are a bit of a mixed bag. Some of the major characters follow stock archetypes typical of shounen battle anime as Xin feels too much like the hot-headed, dense and battle-loving action hero that the genre loves to milk and He Liao Diao mostly serving as a sidekick character. Many of the battles in the series also have the feel typical of a shounen battle anime with characters blindly charging into battle and taking plenty of punishment in fights, yet continuing to persevere and eventually overcome their foes. Not helping matters with the battles in the series are the show's awkward efforts to mix its regular animation, with CG animated sequences that are quite glaring to see when scenes switch between the different animation styles and the fact that the rendering of characters in said CG sequences look quite rough compared to the regular animation.
On the plus side, the historical elements implemented into Kingdom allow its storytelling to have some elements of sophistication that give it a smidge more depth compared to most shounen battle titles. A number of characters are given a good deal of dimension and depth to explore their personalities and what drives them in making the decisions they do. The developments in a decent chunk of Kingdom's first half lead to growth in the characters of Xin and Zheng. Also with the great deal of focus on planning for warfare provided at a number of points in the series, the more battle-savvy leaders in the series are shown to deploy a good amount of tactics and strategy when leading their squadrons against enemy threats.
In spite of the praises though, Kingdom suffers quite a bit in having an uneven focus with how it wishes to portray itself between wanting to be a historical war title dabbling into military strategy and famous figures of the Chinese Warring States period or a shounen battle anime that dabbles into a number of the typical cliches of the genre. If Eastern historical anime titles grab your interest, Kingdom is certainly not one of the best offerings of the genre and I would certainly not be in favor of watching it more than once.
