Since the Sui Dynasty, Koguryo (高句丽) had been called Koryu (高丽), and its capital had been Pyongyang (平壤). Sui Yang-Emperor (隋炀帝) started several wars against Koryu, but the Sui Empire couldn’t capture this strong country. The last straw of the fateful rebellion which was against the Sui Empire was the war of Koryu.
In A.D. 618, the Tang Empire was built. Gao Jianwu (高建武), the new king of Koryu and the younger brother of Yuan (元), was friendly to the new empire, and paid tribute to the Tang Dynasty. Tang Gao-Zu (唐高祖) demanded to interchange prisoners of the past wars. More than one hundred thousand prisoners were returned courteously to the Central Nation. Tang Gao-Zu was a kind-hearted man, and he said to his ministers, “I only want to bring peace to my people, and I don’t want Koryu to submit itself to us. We don’t need false pride.” However, many ministers said, “The territory of Koryu belonged to our nation in the history, so we can’t permit Koryu not to submit itself to us. The Central Nation and the foreign nations are as the sun and the stars, so we can’t deign and treat them equally.” Then Tang Gao-Zu abandoned his idea. In fact, the idea of Tang Gao-Zu was right. False pride often caused the Central Nation not to know about foreign nations, and false pride brought too many tragedies to Chinese people. Nowadays, false pride still remains in the heart of some persons. We must be alert to the kind of mind.
In A.D. 631, Tang Tai-Zong (唐太宗), the son of Tai Gao-Zu, sent a minister to go to Koryu and take back the bones of the dead armymen of the Sui Dynasty. This envoy and his attendants destroyed the “Jingguan” (京观) which was built for showing military achievements against the Central Nation by Koryu. Jianwu heard this news, and he was very afraid that the Tang Empire would revenge the past insult. So Jianwu built long walls in the border. In A.D. 640, Jianwu sent his heir to pay tribute to the Central Nation, and Tang Tai-Zong treated him very well. In A.D. 642, Suwen (苏文), a minister of Koryu, killed Jianwu and let the nephew of Jianwu ascend the throne. Tai Tai-Zong thought Jianwu was loyal to his empire, so he felt very sad. In A.D. 643, Tai-Zong sent an envoy to go to condole and confer the title “the king of Koryu” to the new king of Koryu. At that time, Koryu often invaded Silla (新罗) which was a country in modern-days South Korea. Silla was friendly to the Central Nation, so the envoy of China advised Suwen not to attack Silla, but Suwen refused to accept the mediating of China. Tang Tai-Zong thought it was necessary to show his prestige to Koryu. So he decided to attack Koryu.
In A.D. 645, Tang Tai-Zong sent forty thousand armies to cross the sea by five hundred battleships from Laizhou (莱州, this area belonged to modern-day Shandong Province), and he sent the land army of sixty thousand men entered Liaodong (辽东, the east of modern-day Liaoning Province) which was captured by Koryu in A.D. 404. The two armies joined in the north of Koryu. Tang Tai-Zong went to command the troops by himself. The army of Tang Empire advanced successfully. In the fourth month (Lunar Calendar) of this year, the army of Li Ji (李勣) seized Gaimou (盖牟, the area belonged to modern-day Shenyang of Liaoning) City and captured twenty thousand people of Koryu. In the fifth month, the army of Cheng Mingzhen (程名振) seized Shabei (沙卑, the area belonged to modern-day Dalian [大连] of Liaoning) City and captured eight thousand people of Koryu. The army of Li Ji started to attack Liaodong City (辽东城, modern-day Liaoyang [辽阳] City of Liaoning Province). Koryu sent forty thousand armymen to aid the defending troops of Liaodong, but Li Daozong (李道宗) led four thousand cavalry men to defeat the reinforcements of Koryu, and killed more than one thousand armymen of Koryu. In the battle of Liaodong City, the army of Tang Empire used many military engines (抛车) which could hurl stones of 300 Jin (斤, In the Tang Dynasty, 1 Jin was equal to about 640 g) to the targets outside 1 Li (里, In the Tang Dynasty, 1 Li was equal to about 540 m), and destroyed the fortifications of Koryu. They also used colliding engines (撞车) to destroy the buildings of Koryu. The armymen of Tang set fire to the buildings, and there was fire everywhere in the city. More than ten thousand people of Koryu were burned, and more than ten thousand armymen of Koryu were captured. The Liaodong City was seized by the army of Tang.
In the sixth month of A.D. 645, Baiya (白崖, the area was between modern-days Anshan [鞍山] and Benxi [本溪] of Liaoning) City surrendered, and the army of Tang captured ten thousand people and two thousand and four hundred armymen of Koryu. The army of Tang started to attack Anshi City (安市城, Modern-days Haicheng [海城] City of Liaoning Province). Gao Yanshou (高延寿) and Gao Huizhen (高惠贞) led fifteen ten thousand armymen of Koryu and Mohe (靺鞨, a nomadic nation of the Northeast Asia, the ancestors of the Manchus) to aid Anshi City. Tang Tai-Zong led his army to attack the reinforcements of Koryu by himself and killed more than ten thousand enemies. Gao Yanshou and Gao Huizhen surrendered. Three thousand and five hundred chiefs of Korean tribes were captured. The army of Tang Empire got thirty thousand horses, fifty thousand cattle, five thousand armors and a large number of weapons. Three thousand and three hundred armymen of Mohe were buried alive. In the eighth month, Li Ji caused Gao Yanshou to induce the defending troops of Anshi City to surrender, but the defending troops refused, and they uncompromisingly resisted the army of Tang. Tang Tai-Zong was very angry, and Li Ji said, “Please permit us to kill all of the men of Anshi when we capture the city.” The people of Anshi City heard the words, and decided to fight to the death. The armymen of Tang Empire used many hurling-stones engines and colliding engines to attack the city, the people of Anshi City still kept their city.
The late autumn came, and the weather was very bad. The armymen of Tang were from the Central Plains, and they couldn’t adapt themselves to the very cold weather. The supplies were spent. Tang Tai-Zong had to withdraw his army.
Tang Tai-Zong was a kind-hearted emperor. When the Liaodong City was captured, fourteen thousand captured people of Koryu were released, and these people cheered in three days.
In 646, Koryu sent envoys to apologize for the past offence, and presented two beautiful women. However, Tang Tai-Zong refused to accept the two women.
In 648, Tang Tai-Zong sent Xue Wanche (薛万彻) to lead army to cross the sea and enter the Yalu River (鸭绿水). The army seized the Bozhuo (泊灼, modern-days Dandong [丹东] of Liaoning) City of Koryu, and got a large number of captures. Tang Tai-Zong ordered to build big ships, recruit brave men, and prepare supplies and weapons for the future war against Koryu. However, in the next year, the great emperor died, and he couldn’t realize his plan.
In 650, Tang Gao-Zong (唐高宗), the son of Tang Tai-Zong, ascended the throne. In 666 (乾封元年), there was a civil strife in Koryu. The son of Nansheng (男生) who was the eldest son of Suwen ran away to Tang Empire and asked for helping his father. Tang Gao-Zong sent an army to aid Nansheng so that Nansheng could run away to the Central Nation. In the eleventh month (Lunar Calendar), with the suggestion of Wu Zetian (武則天) who was the wife of Gao-Zong, Tang Gao-Zong sent Li Ji to lead army to attack Koryu.
Li Ji (李勣) was a famous general of the Tang Dynasty. The original name of Li Ji was Xu Shiji (徐世勣). Because of his military achievements, Tang Tai-Zong conferred the royal surname Li (李) to him. After the death of Tang Tai-Zong, Li Shiji (李世勣) changed his name to Li Ji in order to hold Tang Tai-Zong in respect, because Tang Tai-Zong’s name was Li Shimin (李世民). Li Ji was loyal to the royal family of the Tang Empire, and he also supported Wu Zetian to be an empress. Of course, Wu Zetian also respected this old general. Li Ji died at the age of 76 in 669. Later, his grandson Xu Jingye (徐敬业) rebelled against Wu Zetian became an emperor but failed, and then his whole family was killed by Wu Zetian. When Tang Zhong-Zong, the son of Tang Gao-Zong and Wu Zetian, ascended the throne, the honor of Li Ji and his family was restored.
Li Ji was an excellent commander, and his army seized the enemy’s cities so easily like splitting a bamboo. In the ninth month of A.D. 668, the army of the Tang Dynasty besieged Pyongyang (平壤), the capital of Koryu. An officer of Koryu opened the city gate, and the armymen of Tang rushed into the Pyongyang City. There were street battles between the armies of Koryu and Tang. In the eleventh month, Pyongyang was completely captured. Later, the army of Tang captured other cities of Koryu. Then the whole Koryu was captured by the army of Tang Empire. The imperial government built an administrative district called “Andong Duhu Fu” (安东都护府) in Koryu, and Pyongyang was renamed “Andong” (安东). Xue Rengui (薛仁贵), a famous general as Li Ji, became the Duhu (都护, the title of the prefect of this district). Many chiefs of Korean tribes were appointed to officials, and helped the officials of the Central Nation to manage the land of Koryu.
Gao Zang (高藏), the king of Koryu, was sent to the Chang’an (长安, modern-day Xi’an) City, the capital of the Tang Empire. In A.D. 677, Tang Gao-Zong gave him a title “the King of Joseon” (朝鲜王) and let him return to Andong. However, when Gao Zang arrived at Andong, he actually planned to rebel with Mohe tribes. The intrigue was shattered soon. The imperial government recalled Gao Zang and exiled him to Qiongzhou (邛州, Modern-days Chengdu City of Sichuan Province).
The land of Koryu was not placid. In A.D. 662, Paekche (百济), a country in modern-day South Korea, was weakened utterly by the armies of Tang and Silla. Silla nibbled the territory of Paekche and finally annexed this country. When the army of Tang captured Koryu, Silla started to abet the people of Koryu to rebel against Tang Empire. In A.D. 669, there were rebellions in several cities. The army of Tang tried to suppress the rebellions. In the battle of Anshi, the rebel army of Koryu was defeated. In the battle of Quanshan (泉山), two thousand armymen of the reinforcements of Silla were captured. In the battle of Falu River (发庐河), about ten thousand rebels were killed or captured. The other rebels had to run away to Silla. After four years, these rebellions were suppressed. However, the new rebellions started again with the aid of Silla. After the military suppressing of a long time, Korean still resisted stoutly against the occupancy of the Tang’s army. Tang Empire had to decide to withdraw the army. In A.D. 676, the official seat of the Andong Duhu Fu moved from Pyongyang to Liaodong City. In A.D. 677, the official seat moved to Xin City (新城, Modern-day Fushun [抚顺] City of Liaoning). In A.D. 735, Tang Xuan-Zong (唐玄宗) acknowledged that the Pei River (浿水, Modern-day the Taedong River [大同江]) was the border between the Tang Empire and the Silla Kingdom. In the later years, while the Tang Empire declined, Silla nibbled the areas of the north of the Taedong River and finally ruled the whole Korea Peninsula.