Sui Yangdi -- a very special emperor

[Ian_Lee]

The second emperor of Sui Dynasty -- Mr. Yang Guang -- whose label was Yangdi, was a very special emperor.

What was so special about Mr. Yang?

Mr. Yang set a record in squandering all the goodwills, assets, wealth, reputation,....etc in a record breaking pace -- only 13 years.

When his father -- Wendi died -- Sui Dynasty was at its peak.

Sui concluded a long divided period in Chinese history and for the first time gave peace to the people under a unified country. Everyone yearned for stability. At the time of Wendi's death, the granary was full. There was no great external threat. And for first time in history, Japan sent its students to Sui to study.

So what made Yangdi lose his mandate in merely 13 years?

In Chinese history, there were similar cases that the second emperor lost his throne or even the country. But those cases happened under certain circumstances:

(1) Son of Qin Shihuang -- He lost the empire because most people suffered enough under Shihuang.

(2) Son of Zhu YuanZhang -- the second Ming emperor lost his throne because his uncle was too powerfu.

But Mr. Yang Guang did not belong to either category. His father accumulated strong goodwill among the populace. No members in the Royal family could challenge him. And Mr. Yang was an adult when he took over the throne. He had military experience in conquering the southern Chen Dynasty.

And Mr. Yang seemed not to be too addicted to women since he killed the beauty of Chen Dynasty -- Ms Zhang Li Hua (He blamed her for making Chen Emperor lose the dynasty)

Mr. Yang forced the people to build the Grand Canal and cruised there twice. But would only that infrastructure project force the people into open mutiny?

[bhchao]

Yangdi's military excursions into Koguryo also took a toll on the Sui. Despite being outnumbered, Koguryo beat the Sui forces so badly that Sui was left permanently ruined.

Mr. Yang set a record in squandering all the goodwills, assets, wealth, reputation,....etc in a record breaking pace -- only 13 years.

Sounds like a familiar president from today, except that it was done in less than 3 years. In comparison, Yangdi should get a posthumous medal.

[bhchao]

Recently there has been a row between China and South Korea over the ancient kingdom of Koguryo. China claims that Koguryo was a province of China, which has infuriated both North and South Korea.

South Korea has considered options such as recalling its ambassador to China or starting relations with Taiwan if Chinese academics revise their textbooks to include Koguryo in China's sphere. Some Koreans even rooted for Japan during the Asian Cup final.

History is not on China's side. Koguryo, Silla, and Paekche have always been independent from China's rule, and only paid symbolic tributary status to the Chinese empire. In fact, the might of Koguryo prevented numerous Chinese attempts to take over the kingdom and endanger the entire Korean peninsula. Koguryo's military successes against Sui Yangdi, especially under the leadership of General Ulchi Mundok, and its successes later against Tang Taizong, were instrumental in preserving Korean cultural identity up to the present time.

Koreans might have been assimilated into the Han race (Just like Manchus today are not an independent concept) had it not been for Koguryo's military successes against Sui Yangdi and Tang Taizong. It was only with the help of the Korean kingdom Silla that Tang China was finally able to defeat Koguryo in a two-front war; Tang hitting Koguryo from the north and Silla hitting Koguryo from the south. After the collapse of Koguryo, Tang China then tried to incorporate Silla into its sphere of influence. Silla rallied the peoples of Paekche and former Koguryo, and drove the Tang forces out of the Korean peninsula altogether.

[Ian_Lee]

Bhchao:

Read the previous thread on Pohai/Parhae:

http://www.chinese-forums.com/viewtopic.php?t=988

[bhchao]

Ian, thanks for the reference to that thread. Didn't know you had posted a topic earlier on Koguryo.

I find it ludicrous that the Communist government considers Koguryo a previous province of China.

[Ian_Lee]

Bhchao:

PRC does everything for a purpose.

I guess it is now preparing for the implosion of North Korea. By rewriting history to reclassify Koguryo, an ancient kingdom which territory straddles across both present day China and North Korea, as a Chinese kingdom -- it provides PRC with legitimate excuse for the future political, and perhaps military, intervention in case North Korea implodes.

[skylee]

The following quotes on the relationship between China and Korea are from 中國人史綱 of 柏楊 (they are copied from this webpage, one of its many on-line versions in simplified chinese). What do you think?

(商紂帝)子受辛的叔父子胥余于朝歌陷落时，逃到朝鲜半岛，建立朝鲜的第一个王朝，称箕子王朝，也称箕子朝鲜。

东方，指朝鲜与日本。

　　

高句丽王国在本世纪（七）初，抵抗中国隋王朝攻击之前，南端的新罗王国（韩国庆州）曾占领它纵深二百五十公里的土地。四十年代后，高句丽王国发生政变，宰相（莫高支）泉盖苏文把国王高建武杀掉，另立高建武的侄儿高藏当国王，由泉盖苏文专政。他需要用对外的军事胜利以增加威望，于是跟半岛南端的另一王国百济（韩国扶余）联盟。于六四四年。向新罗进攻，宣称索回失去的国土。但连陷四十余城而仍不停止，显然的它要全部咽下去。新罗王国向中国告急。中国命高句丽停战，泉盖苏文拒绝。明年（六四五），李世民大帝亲征，那座杨广倾全中国之力不能攻陷的辽东城（辽宁辽阳），终被攻陷。接着连破白崖城（辽宁海城），盖牟城（辽宁盖州），进围安市城（辽宁海城）。安市城在高句丽名将杨万春固守之下，成为第二个辽东，中国兵团百般攻击，杨万春百般防守，终不能攻破。而严冬已至，大地冰封，中国远征军没有御寒装备，不得不撤退。杨万春在城上拜别致谢，李世民大帝命送他绸缎一百匹，表示对他的敬意。这一次的军事行动并不算是成功，但李世民大帝与杨广不同处在此，李世民没有斗气再来。

高句丽在北方失地丧师，对南方新罗的侵略只好停止。但百济王国却不停止，新罗真德女王撰写《太平颂》，亲自刺绣，呈献中国，乞求援救。六六O年，真德女王的继承人金春秋，再向中国告急。中国派遣大将苏定方率海军赴援，舰队从成山（山东荣成）出发，在百济王国熊津江（锦江）江口，强行登陆，百济战败，首都泅批城（韩国扶余邑）陷落，国王扶余义慈投降。中国就把百济收入版图，设立熊津等五个都督府，苏定方不久率军回国，留大将张仁愿镇守。

苏定方刚走，百济的高僧道琛和大将福信，就迎接当时在日本的太子扶余丰回国，继承王位，包围泅批城中国驻屯军。明年（六六一），中国大将刘仁轨增援，也在熊津江口登陆，百济军迎战，大败，泅批城之围解除，退保周留城（韩国韩山）。刘仁轨所率的兵力不多，不能进攻，只能帮助张仁愿坚守泗氵比，僵持两年之久。六六三年，日本大军入援百济，中国再派大将孙仁师渡海增兵，另一位大将刘仁轨率海军从熊津江进入白江（韩国锦江），准备跟孙仁师会合后进攻周留城。想不到就在白江口，与日本入援的海军舰队相遇，遂行决战。中国舰队猛烈锲入日本舰队的腰部，日本舰队被从中切断，首尾不能相应，只好边战边退。中国不断冲击，四战四捷，击沉和焚烧日舰四百余艘，烟火冲天，海水都化成血水；日本舰队全军覆没。这是中国跟日本第一次战争。扶余丰得到败讯，知道大势已去，放弃周留城，向北逃往高句丽王国。百济王国立国六百八十一年而亡。

高句丽王国宰相泉盖苏文于六六六年逝世，儿子们爆发激烈的夺嫡斗争，嫡子泉男生失败，投奔中国。一个无比坚固的国家，外部历无数严重打击，都没有使它崩溃，如今却从内部裂开。中国抓住这个机会，派大将李(责力)当总司令，泉男生当向导，由陆道东征。六六八年，攻陷首都平壤，国王高藏被俘。高句丽王国立国七百零五年而亡，朝鲜半岛的三国时代结束。

现在，朝鲜半岛四分之三的土地入于中国，新罗王国局促在半岛东南角四分之一的土地上。不过中国统治的时间只有九年，新罗王国对中国并吞了那么多土地而竟没有分给它一点，深为不满。这个忘恩但勇敢的小国，开始暗中向庞然大物的中国挑战，到处发动民变，促使平壤孤立。六七六年，中国驻屯军不能支持，只好撤退，把设在平壤的安东总督府迁到辽东（辽宁辽阳），新罗王国遂统一朝鲜半岛的中部和南部，隔着氵贝水（朝鲜大同江），跟中国为邻。

新罗王国统一半岛中南部后，并没有继续跟中国对抗，反而非常明智地采取事大——事奉大国政策，对中国十分恭顺。这个政策获得完美的效果，从此中国和朝鲜之间，再没有战争，永为手足般的兄弟之邦。

高句丽王国灭亡后三十年，即本世纪（七）最后一年（六九九），它的一位流亡在北方松花江流域的大将大柞荣和他率领的一部分武力，跟当地(革末)(革曷)部落结合，建立渤海王国。跟朝鲜半岛上的一些国家一样，全盘华化。官制官名，以及政府组织，与中国无异。它对中国也采事大政策，所以中渤之间，邦交敦睦，从没有战争。

大祥荣最初称他建立的王国为震王国，下世纪（八）七一三年，中国册封大祥荣为渤海郡王，才开始改用渤海作为国名。

日本帝国，跟朝鲜半岛上诸国同样古老，但那时候文化却比朝鲜落后，因为中国文化必须经过朝鲜，才能传入日本。本世纪（七）之前，日本仍是部落形式的结构，但在中国绝对优势的文化冲击之下，日本固有的一切，已不能适应国内的需要和崭新的国际局势。于是产生现代化——即中国化运动。六四六年，孝德天皇下令把全国土地从贵族手中收回，改为国有。废除类似奴隶主的世袭官爵制度，使全国人民不再隶属贵族，而直接隶属天皇。效法中国办法，贵族只有封爵，没有土地。改用中国国特有的“年号”制度，定本年（六四六）为大化元年。依照中国政府三个“省”的形态，组织日本政府，设立六个（省），分别掌理国务。并普及教育，采取中国文字为法定文字，以孔颖达的《五经正义》为法定课本。这是日本第一次大规模接受现代化文化运动，史学家称“大化改新”。从此，日本跟朝鲜半岛诸国一样，成为中国之外的另一个“中国”，无论文字、教育、官制、政府，甚至意识形态和中国几乎完全相同。

—— 日本的中国化运动，大化改新只是起步。从此之后，对中国文化的吸收，一千余年间，与日俱增。因之普遍地产生一种中国崇拜，认为日本一切都是错的，中国一切都是对的。若干著名的学者甚至认为中国的改朝换代才合乎经典，而日本天皇万世一系制度，是一种可耻的谬误。日本人最初以夷狄自居，尊奉中国是中国，后来则自以为日本才是中国，中国反而成了夷狄。平安时代（七九四——一八五）名诗人赖忠传，曾有诗说：“乘船当乘作文船，扬名无逾作汉诗。”可说明日本对中国倾慕的程度。

张居正死后不久，日本大举侵略朝鲜王国，中国第一次武装援助朝鲜。

朝鲜王国和安南王国，是中国南北两个最忠实的藩属，他们除了有一位国王和使用一种跟中国大同小异的文字外，事实上可以说是中国的一省。中国是他们的保护者和宗主国，但从不过问他们的内政。

日本帝国在本世纪（十六）有一位巨人崛起，他就是平民出身的大将丰臣秀吉。他统一了全国，担任国家最高执政官（关白），天皇便成为一个虚名。丰臣秀吉在国内建立了不朽的功业后，日本三岛已不能容纳他的野心，他决定征服朝鲜。

...

第二年(一五九二），丰臣秀吉统率海陆军十五万人，渡过对马海峡，在朝鲜半岛的釜山城登陆。朝鲜不堪一击，日军长驱直入，抵达首都王京（汉城）。王京陷落，国王李(日公)逃到北方的开京（开城）。开京又陷落，又逃到更北方的平壤。平壤又陷落，李(日公)于是逃到跟中国一水之隔，鸭绿江畔的义州。日本兵团自四月在釜山发动攻击，到六月夺取平壤，只不过三个月时间，朝鲜全国八省（道），全部失守，只剩下义州一个孤城。李(日公)向中国告急，他认为复国无望，请求举族内迁。

中国这时正逢宁夏军区(口孛)拜兵变，兵力集中在西疆，一时不能调遣。国防部长（兵部尚书）石星就派遣精通日本语文的沈惟敬，作为中国使节，前往日本占领下的平壤，了解情况。沈惟敬到平壤后，日本大将小西行长表示：“日本无意跟中国为敌，我们愿跟中国共同瓜分朝鲜，以大同江为界。中国如果同意的话，日本就撤出平壤，退到大同江以南。”沈惟敬回报，中国拒绝，认为必须维持朝鲜领土的完整与主权的独立。这一年九月，(口孛)拜事件平息，中国大将李如松率援朝军出发。

李如松于十二月渡过鸭绿江，跟国王李(日公)会合。明年（一五九三）正月，开始进攻，张居正整顿后的武装部队，仍有残存的优良纪律和战斗力，日军大败。援朝军追击三百余公里，克复平壤。再追击一百五十余公里，克复开京（开城）。日军节节失利后，在王京（汉城）北十五公里碧蹄馆，布置埋伏，由间谍向李如松报告说：“日本人已放弃王京，向南逃窜。”李如松这时已经被胜利冲昏了头脑，十分骄傲。他轻骑急追，在碧蹄馆陷入重围，战马跌倒，他的头部受伤，虽然援军仍将日军击退，但损失惨重，锐气已消。

然而，日本也无力反攻，而且鉴于平壤之败，不敢固守后勤交通线有随时被切断危险的孤城，不久真的放弃王京（汉城），撤退到朝鲜半岛南端最初登陆地的釜山。丰臣秀吉返回日本，留下小西行长：等候命令。这时除了釜山一城外，朝鲜全国光复。如果换了有些大国，可能会趁此良机，把朝鲜一口并吞。然而中国却命国王李(日公)不必内迁，还都王京（汉城），李(日公)像中了马票一样的大喜过望。

日本退守釜山后，中国援朝军在外围布防。国防部长石星主张谈判解决，国王李(日公)也向中国要求如此。这件艰难的工作由沈惟敬担任，最后中国允诺加封丰臣秀吉为日本国王，并允许日本贸易，日本则允诺撤出釜山。一五九六年，中国派遣使节团前往丰臣秀吉所在地大阪（当时日本首都仍在京都），举行册封典礼，朝鲜也派一个代表团陪同观礼。然而，日本的谈判不过是一个骗局，丰臣秀吉需要时间重新集结兵力。我们一眼就可看出，他不能接受日本国王的封号（好像连精通日本语文的沈惟敬，也不知道日本还有一个高高在上的天皇）。于是等到中、朝两国代表团抵达大皈之后，丰臣秀吉指摘两国代表团的代表，官位太低，礼物也太薄，不但瞧不起日本，也瞧不起中国。一方面要求中国惩罚朝鲜，一方面在釜山发动第二次攻势。

...

一五九八年，即本世纪（十六）最后第二年，丰臣秀吉在大阪逝世，遗令退军，留在釜山的日军才行撤退。其实即令丰臣秀吉不死，日军因粮道不绝如缕，也会撤退。但丰臣秀臣之死，使他们撤退有名，保持了颜面。

—— 七世纪时，日本出兵朝鲜半岛，还可以说是援助百济王国对抗新罗王国。本世纪（十六）这一次，则连一个借口都没有，而是赤裸裸最原始性的对外侵略。假如不是中国干预，朝鲜早已灭亡。日本似乎总是气咻咻的，稍微有一点力量，就企图奴役他的邻国，不管这邻国对他多么友善。

这是日本第一次侵略朝鲜，也是中国第一次保卫朝鲜，自一五九二年到一五九八年，历时七年。日军撤退后，中国援朝军也跟着撤退。这是历史上国与国之间，最标准的无私援助，中国战士的鲜血，洒遍朝鲜半岛，而一无所求。

朝鲜王国是中国最古老的藩属之一，世界上再没有两个国家能像中国跟朝鲜这么长期的密切融洽。中国为保护朝鲜付出了巨大的代价。过去的事我们已叙述过，到了下世纪（十九），中国又为他作出第二次更大的流血牺牲。

What happened in the 19th century was 甲午戰爭 and 馬關條約, which started from a war in Korea.

中国战败，朝鲜陷于惊恐，在朝鲜人的眼中，伟大的天朝是不会战败的。朝鲜失去了靠山，六神无主，只有默默地承认日本为他们的宗主国。

—— 本世纪（十九）最后第三年（一八九七），日本命朝鲜国王改称皇帝，并改称为大韩帝国。下世纪（二十）一九一○年，即清政府被中国人推翻的前一年，日本命李照签订跟日本《合并条约》，朝鲜遂亡。朝鲜当中国的藩属一千余年，两国感情融洽，如足如手，中国对朝鲜没有任何领土野心，这一次又为了保护它，而连自己的领土都赔了进去。但它当日本的藩属只不过十六年，就被并吞。

[bhchao]

Sui Yangdi also had an obsession with the south and frequently vacationed there. He even went there to indulge himself as the Sui dynasty was disintegrating. The fact that he was assassinated in his bath at Yangzhou is not surprising.

His mother 隋文帝皇后 獨孤氏 was a neurotic Buddhist Dugu woman who even intimidated Yang Jian. Her influence probably scarred poor Yangdi. His mother was also the sister of Li Yuan's wife.

Yangdi also allegedly killed his father with his own hands. Simon Li didn't sorry, Skylee

And Mr. Yang seemed not to be too addicted to women since he killed the beauty of Chen Dynasty

There is a big contrast between Yangdi and Li Yuan. As you mentioned, the former didn't seem too enthusiastic about women. Li Yuan on the other hand was reported to have rebelled against Yangdi after sleeping with one of his master's concubines. He also rebelled at a time when it was safe to do so, when Sui was disintegrating. So Li was prudent. Yangdi was not.

A difference between the Yangs and the Lis was that they were on slightly opposite ends of the ideological spectrum. The Yangs tilted more towards Buddhism, while the Lis (with the exception of Tang Taizong) were more Confucianist.

[Ian_Lee]

Even though Sui Dynasty is a blink in Chinese history, it has accomplished two major feats:

(1) Like Qin which unified China after long term disintegration, Sui also was a dynasty that unified China after 400-year division. And if Sui didn't reunify China, there was the possibility that China might have forever be divided into two halves since the difference in culture and ethnicity was quite huge at the end of that 400-year period.

(2) Like Qin which had the architectural feat of Great Wall, Sui also had the architectural feat of Grand Canal.

Interestingly Sui is more frequently mentioned in Japanese history because formal contact between China and Japan started in Sui Dynasty. Japan sent 遣隋使 (the envoy to Sui) 小野妹子 during Yangdi's reign.

[holyman]

He had military experience in conquering the southern Chen Dynasty.

yangdi's military campaign were always in a same pattern, outnumbering the enemy with overwhelming forces. when he attacked the korean peninsula he used the same tactics, amassing the biggest army he had ever commanded, and supplies became a burden to both his ppl and his army. coordination was all out they cannot hit hard enuff and effective enuff. koguryo on the other hand was pretty much united and had a higher morale. in the end yangdi lost after a brief contact and retreated hastily, leaving tons weapons and supplies behind for koguryo.

[bhchao]

Like Qin which unified China after long term disintegration, Sui also was a dynasty that unified China....Like Qin which had the architectural feat of Great Wall, Sui also had the architectural feat of Grand Canal.

Both were also short-lived, repressive dynasties who laid everything in place for the next dynasty. Without retaining Qin's bureaucratic structures, Han would have no strong foundation to rest on. The only difference between the two were the governing styles and policies of each dynasty.

The same can be said of Sui-Tang. Li Yuan did not have to worry about unification or developing infrastructure because Yang Jian and Yangdi (although irresponsible and decadent), had already done everything for him, such as the Grand Canal.

The foundations that Sui laid was the backbone which enabled Tang Taizong to pursue his expansionist foreign policies.

So the nasty work that Sui implemented helped Tang in the long run by enabling the latter to concentrate on economic, foreign, and cultural agendas.

[skylee]

Recently I have heard some discussions on what if Sui Yangdi defeated Koguryo. Hehehe

Anyways, I have come across this and found it quite interesting ->

說到「怨怨相報」，前人說得有趣。隋文帝楊堅篡掉「外孫」（不是親的）的江山，大肆屠戮北周宇文家遺裔，結果兒子隋煬帝楊廣卻死在宇文化及手上。李淵父子掃平隋末群雄，得了楊家的天下，後來楊家出了楊國忠、楊玉環兄妹，將唐玄宗李隆基親奠的盛世破壞，迫出「安史之亂」，成為中國史上的一個分水嶺，影響往後數百年的歷史。當中的「因果」也真巧合！

Any views? Were Yang Guozhong and Yang Yuhuan really descendants of the Sui royal family?

[bhchao]

Recently I have heard some discussions on what if Sui Yangdi defeated Koguryo.

If Sui Yangdi defeated Koguryo, Silla and Paekche would have fallen as well, and the whole Korean peninsula would have come under Chinese control.

That was the first real crisis the Koreans faced regarding their national identity and they passed with flying colors. Koguryo humiliated Sui Yangdi and bruised Tang Taizong when the latter sought revenge.

The second crisis came right after the combined Tang-Silla force defeated Koguryo. Like Sui, Tang cannot defeat Koguryo on its own. So it had to seek help from another Korean kingdom by forming an alliance with Silla. After the alliance defeated Paekche, Tang attacked Koguryo from the north and Silla attacked from the south.

Koguryo collapsed and Tang took control of the former kingdom. But Tang's intention in the first place was to bring the entire Korean peninsula under Chinese control, which means targeting Silla as well. Silla realized this and almost immediately after Koguryo collapsed, Silla rallied Korean forces and kicked the Tang forces completely out of the Korean peninsula altogether.

Korean culture would not have developed unhindered had Sui Yangdi defeated Koguryo, and had Silla not been able to defeat the Tang Chinese forces. It would be very difficult to develop a distinct culture had the entire peninsula fallen under Chinese control.

Out of 300,000 Sui troops dispatched to Koguryo, only 2,700 made it home alive. (90% of the Chinese force were destroyed by Koguryo). So you can imagine Tang Taizong's thirst for revenge.

[skylee]

Korean culture would not have developed unhindered had Sui Yangdi defeated Koguryo, and had Silla not been able to defeat the Tang Chinese forces. It would be very difficult to develop a distinct culture had the entire peninsula fallen under Chinese control.

Yeah this is what those discussions were about, which made people blush. 癡人說夢 IMHO, but you can see what some people think/want/dream ...

[bhchao]

Another good question would be what if Tang Taizong had not died just before embarking on a final expedition against Koguryo.

Here is a good animated timemap showing the development of Korea's Three Kingdoms period coinciding with Tang movements in Korea.

http://www.timemap.net/epublications/2002_animations/2002_shilla_animation.swf

[bhchao]

Another thing worth noting:

Ulchi Mundok's leadership of the Koguryo army and his actions against the Sui army was classic Art of War. On the other hand, everything that Sui Yangdi did against Koguryo were actions that ran contrary to what Sun Tzu wrote in the Art of War.

Sui Yangdi thought he could defeat Koguryo by overwhelming force alone. He seriously underestimated the resolve of the Koreans.

One example, Sun Tzu wrote "Know thyself and know your enemy, and you can win over a hundred battles". Mundok obviously had that mindset, Sui Yangdi didn't.

[skylee]

Sun Tzu wrote "Know thyself and know your enemy, and you can win over a hundred battles".

知己知彼，百戰不殆﹔不知彼而知己，一勝一負﹔不知彼不知己，每戰必殆。

[Ian_Lee]

Bhchao:

My interpretation of Korean history is a little bit different from you.

There could hardly be any Korean national identity developed until the unification of the Later Three Kingdom by Koryo. Before that, the present-day Korean peninsula and Liaodong region had been in separate administration of three different kingdom for 400-600 years.

And before this period, part of the Korean peninsula was under the direct rule of Han Dynasty while the other parts were half primitive, half legendary chieftain-led kingdoms.

So how could Korean national identity exist before that?

Regarding the joint conquest of Koguryo by Tang-Silla, it was the king of Silla 金春秋 who decided to seek help from Tang first. And in the campaign, it was the Tang forces that captured Koguryo and even established the city of Pyongyang.

And though later Tang pulled out, no succeeding Korean regimes could ever retake the land north of Yalu -- the bulk of Koguryo's original territory.

And Silla culture was almost a duplicate of Tang culture with thousands of Silla scholars and students expatriating in Tang China..

[bhchao]

You're probably right that Korean national identity did not exist at the time of the Sui-Tang invasions of the Korean peninsula. Otherwise the Three Kingdoms would have rallied together to repulse Sui Yangdi and Tang Taizong, but they did not. I think it's debatable when Korean national identity started to take form. Although you could be right about this identity starting to take form during Koryo, I think this national awareness started to develop during the Unified Silla years from 680 to 938.

Korea was divided up into three commanderies by Han Wudi. Before the Han incursion into the peninsula, Korea was consisted of primitive tribes. The Han armies did help bring high civilization onto the peninsula.

Actually Sui and Tang were trying to imitate Han Wudi's success in Korea 600 years earlier, and thought the Korean peninsula was a part of the Chinese empire, just like it had been during Wudi's reign. Korea was already too civilized and independent for them to repeat that feat.

[bhchao]

And in the campaign, it was the Tang forces that captured Koguryo and even established the city of Pyongyang.

Tang forces did capture Pyongyang, but Pyongyang was already the capital of Koguryo when Sui Yangdi tried to capture it during his futile campaign. Regardless of who initiated the Tang-Silla alliance, Tang could not have defeated Koguryo on its own.

And though later Tang pulled out, no succeeding Korean regimes could ever retake the land north of Yalu -- the bulk of Koguryo's original territory.

Silla did not attempt to retake the land north of Yalu. Although I could be mistaken, it was not Silla's original intention to do so.

After Tang invaded Silla, Silla pushed Tang forces northwards and regained Koguryo territory up to the Taedonggang River. It took a while for Unified Silla forces to regain the rest of the Koguryo terrritory up to the Yalu River. Whether they thought of moving beyond the Yalu River is a good question. If Silla had such designs, the modern Korean nation would encompass part of Manchuria.