First, let's clear away some misunderstandings. The story is not about a "last princess" or even a "fallen" noblewoman. It is about a couple of characters who fight for their own visions and aspirations, and who are somewhat fated to be together, despite hurdles and threats to their life.

I was quite satisfied by this drama, despite the sometimes-abrupt editing, which makes suspect parts are missing. But this is understandable since the history of this drama also was not really smooth. As some previous commenters pointed out, it was an adaptation of a novel and in the very long time since it was shot, it got reduced from 50 to 38 episodes, more or less put aside for almost three years, and finally released with little fanfare. Original title is Bu Yun Qu , 步雲衢 (Bù yún qú, which may translate as Crossroads under piling clouds). The original novel was not available to me.

Warning: this is a long review, with History reminders for those unfamiliar with the period. Those who are may of course skip these details.

"The Last Princess" is a historical romance drama set around 1911-1932 from the fall of the Qing dynasty until the end of the warlords’ period and the establishment of the Manchukuo puppet regime in 1931. Despite the grittiness of that Republican era period, it is often the theater for “romantic” movies and dramas using the models of real historical figures, while depicting imaginary characters who might remind of the adventurous ones from Alexander Dumas novels of the 19th century. So, this one is also not a docu-drama, but an imaginary “romantic” story using impressions of some historical characters and events.
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To start, some reminders about Chinese “Republican era “timeline and places may be useful:

* The Qing empire fell in October 1911. A provisional government was established in Nanjing the following year under Sun Yat-sen, who had returned from his long exile to lead the revolution. But the "southern" revolutionaries were not strong enough to defeat the Beiyang army of Yuan Shikai, in the north, who became the de facto dictator of China after the Xinhai Revolution established the Republic of China in 1912.
* The Warlord Era began in 1916 upon Yuan Shikai's death. It lasted until 1927.
* Two of the most powerful strongmen of the Warlord Era were the "Old Marshal" ZHANG ZUOLIN (warlord of Manchuria from 1916 to 1928) and WU PEIFU in Zhili, known as Hebei province, now. (Today, the C-shaped area of Hebei, surrounding Beijing and Tianjin municipalities, makes up the Jing-Jin-Ji megalopolis region bordering the Bohai sea, the Shandong peninsula to the south and the Dongbei north-east region to the north, which borders with the Changbai mountains and the Korean peninsula).
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The drama focuses on the story of a couple, who struggle to fulfill their dreams despite many oppositions

FL character Yurong may appear cold in the beginning, but she does not waver in her sentimental attachment once it is formed, although at times to the point of unreasonable clinging, while also being at times too eager to distance herself from her dangerous warlord. She manages not to appear too unbelievable despite her ever-impeccable hairdo and manicured nails, But her sacrifices for the “public good” are exaggerated and make her stand out sometimes irritatingly as a rigid and stubborn would-be martyr. But not as whiny and childish as another female character (the very irritating Jiaojiao).
28-year-old Rain Wang Herun王鹤润 (who played Yurong) has been acting in many dramas since 2017, including as FL in one (2019 Yanxi Palace: Princess adventures, a Yanxi Palace spinoff)), where she portrayed a determined Qing dynasty princess contending with palace intrigue and a vendetta against her family, while navigating the treacherous terrain of romance. Her portrayal of the conflicted Yurong is adequate. The former princess attempts to become an independent modern woman putting action before passion, sometimes recklessly and clumsily, while she at first remains bound by remnants of old-time family loyalty.

ML character Zhao Zhengnan ( played by 38-year-old singer and actor Ryan Zhang He张赫, who seems blessed with never aging physique) is both handsome and determined: a soldier intent on putting the state before his personal feelings, but still doing his best to protect his love whom he puts before his own life. He manages to reel Yurong in and contain her excesses several times, despite many heartaches.
This was my first time watching a drama featuring this actor born 1984 in Shenyang. A graduate of Shenyang Conservatory of Music, majoring in opera, he is also a singer, but does not sing in this drama. He made his acting debut in the 2009 film “Perfect Bride” and has since taken part in 7 movies and 19 dramas, of which 2 are upcoming. Among these, he was playing, together with Hu Yitian, the role of a war pilot in “Defying the Storm” (a drama set in the period from 1937, when Chinese air force was still in its infancy and relying on foreign planes, sometimes complete with foreign pilots, such as the famous Flying Tigers, an U.S. volunteer squad which operated 1941-1942). I was favorably impressed by his Zhengnan and may look up more of his work.

Special mention to Tao Yi Xi who plays Yurong in the first half of the first episode. She often plays child or support roles since 2013, but we don't know much more about her. She does stand out here, with her kitten!

Each character in The Last Princess represents a part of the turbulent History.

As the descendants of prince Chun did in actual History, the child “gege” (title of a Manchu princess) Yurong decided to cast aside her Aisin-gioro name linking her to the imperial clan, adopting the name Jin (金)instead. (The real-life descendants of prince Chun did the same and lived to become valued professionals and even civil servants in the PRC). From childhood already Yurong set forth to fulfil her dream of becoming a doctor to “help people”. She thus represents the New Women in the beginning of the 20th century.

Yurong was an idealist and stubborn young lady. But at first, she was saddled with a cumbersome family member in the person of Guri Bude, a feckless Manchu cousin to whom she had been betrothed in infancy. She never agreed to fully accept the arranged marriage, living instead as a student housemate or sister, in their Tianjin house near the university where she studied medicine. She was concerned about his numerous weaknesses but without more than a sense of family loyalty to him.
He knew she had a crush on a boy briefly met in her childhood, who might be in Tianjin, but Guri Bude failed to evaluate the importance of this. Guri Bude (played by Zheng Xiaodong) represents the clueless and weak people of the previous regime, who could not defend their spouses, their country or themselves, dreamed of restoration of the Qing empire, but only failed miserably and fell prey to a greedy woman and to opium, the evil drug that led to the downfall of the Qing and invasion of China by foreign powers.

This greedy woman, Baoxi (played by Ke Nai Yu), belonged to the antagonist Wu warlord clan, vying for control of mines and land in Manchuria. The Wu family represents the factions who, in Zhili (present-day Hebei) sided with government only for their own gain, with no sense of honor or of country. Their son Wu Pei (played by "Sean Zhang"/Zhang Liang) was a vicious murderer, ready to kill even his helpers and sell-out to the Japanese who would soon launch a full-fledged invasion after killing the main opponent to their schemes: the Zhao warlord of Manchuria. These were the traitors to the country.

On the other hand, the Zhao warlord was, if not exemplary, at least more likeable, and patriotic. The old marshal cared enough for his son Zhao Zhengnan, main protagonist, that he accepted to cancel another infant betrothal, so Zhengnan might marry his one and only flame. This despite having to forego the direly needed money from the Sheng tycoon family, and make an enemy of Sheng JiaoJiao (played by Chen Meng Qin), the rejected bride-to-be. She would never accept the situation and go to extraordinary lengths to “re-capture” her obsessive life-long interest, Zhengnan.
Meanwhile, beset by lack of funds, the Zhao clan struggled to keep their hold on Fengtian and its rich mining resources. (Fengtian was the name at the time of present-day Shenyang city, and of the province, known today as Liaoning province); another important Manchu name for Shenyang was Mukden, but the drama avoids referring to the game changing Mukden incident of 18 September 1931. It features instead the assassination of the warlord of Manchuria (loosely modeled on real-life Zhang Zuolin, who was murdered by Japanese agents on June4, 1928).

In "The Last Princess", Ryan Zhang /Zhang He plays the role of “Young Marshal” Zhao Zhengnan, loosely based on the historical ZHANG XUELIANG (1901-2001), the so-called "Young Marshal" who became both warlord of Manchuria and head of the Beiyang Government after the death of his father.

The constant power struggle, sometimes armed, between factions in Beijing (Nanjing was official capital in that period) is depicted in this drama. The Beiyang government was changeable and unstable: it had seven different heads of state and more than two dozen different ministries between 1916 and 1928 when China was partly reunified under the Nationalist banner. Foreign influence was important, as despite the capital being in Nanjing, foreign countries also recognized the Beiyang government, pressing it for advantages such as land deals and railroad building and operating. In the decade following 1928, Japanese aggression increased on the coast of Manchuria, which was gradually abandoned by the Guomindang Nationalists. The GMD was more concerned about eliminating their political rivals : the Gongchandang Communist party, following the doctrine of先安内, 后攘外 "first internal pacification, then external resistance" (=getting rid of communists, before fighting the Japanese).

I did not skip any part and was not bored. I will not go into too many details, but here's a bird's view: Zooming to end after many twists and turns, after separations and reunions in cities, on railroads, in hospitals, and in the wild Changbai mountains close to Korea, with bandits! Happy end for the pair, although Jiaojiao got a frightful end, but she was so stupid anyway, that it was a wonder she still was around, and what did she mean, bragging to very end about all the dirt she had on people armed with guns? She really was asking for what she got.

Of course, Manchuria was not yet liberated at end of drama, but the survivors were envisioning peaceful futures. We were spared from gritty depictions of death camps; instead, the cell that held our GCD heroes was surprisingly airy and clean, and I was looking at those handcuffs which slender-wrist Yurong easily could have slid off, and her impeccable clean hairdo with the pearled hair tie... Mmmm looking good till the end! Fingernails always clean and well manicured. THE pin-up heroine! Only found in c-dramas.

Zhengnan also looked dashing in his military uniform, even grazed by bullets that mowed everyone except him. But of course, he still needed to be persuaded to join the Party since this was PRC produced.
(In reality, historical model Zhang Xueliang did not join it, just as he never married a Manchu princess of House Aisin-Gioro, nor a doctor or nurse, for that matter; his real-life personal story was quite eventful, but he was far from a romantic, very different from the Last Princess drama.)

All considered, it was a satisfying melodrama with a handsome cast and mostly OK acting, which I did not regret watching. Since it followed at least more or less the timeline and some features of the Zhang Xueliang historical model, it made me read more to accompany my watching, and I liked the incentive to dig deeper, including watching some documentaries and listening to some period songs, both famous romantic songs by singers like Li Xianglan, the “Liaoning nightingale” (1920-2014) and other ones. These are not featured in the drama, but the OST is soothing and pleasing, and the music is not overshadowing dialogues.
The most memorable song is the one featured on episode end credits: At a glance - 一眼之间 Yīyǎn zhī jiān (Zǐ Zhú 紫竹).
While looking at end credits, I also noticed that there was a musical cooperation with Thailand, including instrumental music directed by well-known Somtow Sucharitkul who is both a gifted writer of horror and science fiction, and a composer (he composed five symphonies and a ballet, a “Requiem: In Memoriam 9/11,” "commissioned by the government of Thailand and inspired by the poetry of Walt Whitman, Emily Dickinson, and T. S. Eliot. ").

You can watch the drama and listen to the complete OST on Youtube https://www.youtube.com/watch?v=nQ2b2Z8Kvi8&t=15s.