Nguyen Van Ngo became emperor and two brothers became vassal kings, and this political structure was not destined to be long-term.

Soon Nguyen Van Hue began to act on his own, sending troops on a northern expedition to Thang Long (Hanoi), overthrowing the Trung clan, meeting with the nominal king Hyeongjong of the Lê Dynasty, and accepting the title of Marshal of Hyunjong as the Marshal of Fuzheng Yi Yun Wei Quoong.

At this time, the infighting of the Tay Son Dynasty began, and Nguyen Van Ngễc was dissatisfied with his younger brother Nguyen Van Hue going north without authorization, so he personally went north and met with Le Thi Tầng (the newly succeeded Emperor of the Lê Dynasty) and Nguyen Van Huy, and agreed that the Lê Dynasty would continue to govern the north, after which Nguyen Van Ngol returned south with his younger brother Nguyen Van Hue.

The elder brother began to worry that his younger brother was too powerful, and the younger brother also became dissatisfied with his elder brother, and soon a civil war broke out between the two sides. During the Ruan civil war, the northern minister Zheng rose up again to control the power of the Li Dynasty, which was allowed to rule the north by the Tay Son Dynasty, and Nguyen Van Hue went on another northern expedition, that is, this northern expedition attracted the intervention of the Manchu Qing Dynasty, and after defeating the Manchu Qing, he was canonized as the king of Annam.

At this time, the Tay Son Dynasty was divided into two parts, north and south, and the eldest brother Nguyen Van Nguyen and younger brother Nguyen Van Hue were each kings.

The brothers' infighting gave the Nguyen Dynasty, which had previously seized the south, the Nguyen Dynasty clan Nguyen Phuc Anh (nephew of the Nguyen Lord) who had been exiled in Siam, with the support of French missionaries and local landlords in the south, returned to China and recaptured Gia Dinh (Ho Chi Minh City). In the years that followed, the Xishan Dynasty had fierce infighting, and he had no time to take care of Ruan Fuying's affairs.

In 1792, Nguyen Van Hue died, and Nguyen Van Hue's son Nguyen Quang Truong succeeded to the throne, called "Emperor Jing Sheng", and honored Nguyen Van Hue as "Emperor Taizu Wu". Nguyen Quang Truong carried out certain reforms to the military regime of the peasant rebel army, appointing a large number of civil and military officials of the old Lê Dynasty, and also adding officials to the generals of the rebel army, transforming the peasant regime into a traditional dynastic regime, and generally consolidating the regime.

At this time, Nguyen Phuc Anh of Gia Dinh (Ho Chi Minh City) had already grown strong and began the Northern Expedition, leading the army to besiege Quy Nhon, the capital of Nguyen Van Viet Nhon.

Nguyen Quang Truong sent a general with 17,000 infantry and 80 war elephants to support by land, and sent a naval army with more than 30 warships to aid Quy Nhhon. Seeing that the situation was strong, Nguyen Phuc Anh led his troops to withdraw to Yanqing Province (Yanqing County, Khanh Hoa Province) and returned to Gia Dinh (Ho Chi Minh City).

However, after Nguyen Quang Truong sent troops to repel Nguyen Phuc Anh, he led his army into Quy Nhon and blocked all the treasury. The eldest brother of the Xishan uprising, Nguyen Van Ngoh, died of anger, and his son Nguyen Van Bao was named a filial piety prince by Nguyen Quang Zhang, known as the small dynasty, and sent Wen Chen to monitor his actions.

At this point, the three fraternal forces that rose in the Tay Son Uprising were one of Nguyen Van Hue's branches, and the biggest enemy they faced at this time was the Nguyen Dynasty of South Vietnam, the Nguyen Phuc Anh clique that they overthrew in their early years.

After a long struggle between the two sides, Nguyen Phuc Anh gradually gained the upper hand. In May this year, the Northern Expedition was renewed, capturing Phu Xuan (Hue), the capital of the Tay Son Dynasty, and the French mercenary Shaino who participated in this battle described it as the most tragic battle between the old Nguyen and the Tay Son Dynasty, and the battlefield was full of corpses. The Xishan army was defeated and dispersed, and the Hua Nan pirates who supported the Xishan Dynasty were also dealt a heavy blow by the Ruan Dynasty army, and the important pirate leader Mo Guanfu, the king of the East China Sea, and the commanders Liang Wengeng and Fan Wencai were captured.

Emperor Nguyen Quang Truong of the Tay Son Dynasty led Dazai Nguyen Quang Sco, Marshal Nguyen Quang Thanh, Grand Sima Nguyen Van Ci and others to flee north, and all the seals and ribbons were captured by Nguyen Phuc Anh. Empress Li Thi Yuping was also captured. The Li family was the princess of the Li Dynasty in the previous dynasty, so the Xishan Dynasty wanted to marry her, and after Ruan Phuc Ying captured her, he did not kill her, and also married her, and accepted Li Yuping as a concubine and canonized as a concubine.

How to deal with these two Vietnamese separatist forces, Zhou Lang discussed with his subordinates, although there was an old matter of Qianlong's canonization of the Xishan Dynasty, most people still supported the Nguyen Dynasty. The reason is very simple, Ruan Phuc Ying is more like a Ming Jun.

Nguyen Phuc Anh took advantage of the internal split of the Tay Son Dynasty and immediately sent Nguyen Van Tien as an envoy to Siam to win the victory, and at the same time expressed his gratitude to Siam for his previous help. Nguyen Phuc Anh rectified the interior of Gia Dinh, prohibiting gambling and witchcraft, while redividing administrative regions and enacting a series of laws to rectify taxation and farming. Nguyen Phuc Anh pursued the policy of "employing soldiers in agriculture" and appointed 12 people, including Zheng Huai Duc, Le Quang Dinh, Wu Cong Zhou, and Huang Minh Khanh, as field officials, and advised them to teach agriculture and mulberry crops, reclaim wasteland, and recruit those who did not want to work as farmers. Nguyen Phuc Anh also actively developed foreign trade and purchased foreign metal weapons; The reduction of tariffs attracted many foreign merchant ships to Jiading for trade.

These measures were in line with the thinking of the landlord class. After the unification of the Tay Son Dynasty, it immediately fell into a split, and after the reform of Nguyen Quang Zhang, the maladministration was not eliminated, and the bureaucratic class of the old Lê Dynasty that caused the uprising continued to be appointed by him, and the generals of the uprising also became new bureaucrats and continued to be powerful.

Therefore, politically, Nguyen Phuc Anh, the magnate of the old regime, is better than Nguyen Quang Binh, the second generation of the leader of the rebel army, not only the Vietnamese landlord forces recognize Nguyen Phuc Anh, but also the ministers under Zhou Lang such as Wang Fuqian also agree with Nguyen Phuc Anh.

Zhou Lang also agrees with Ruan Phuc Anh more, mainly because the Xishan Dynasty encouraged pirates to raid China's coast, even if it has not stopped in recent years, if it weren't for the fact that the country couldn't get out, Zhou Lang would want to fight this warlord.

But who Zhou Lang supports and who he doesn't support, it doesn't depend on personal preferences, he has to calculate interests.

To put it bluntly, whoever gives more benefits, he will support whomever he supports.

But the poor Xishan Dynasty has to rely on pirates to rob, and it is impossible to give Zhou Lang too many benefits, Ruan Fuying has worked hard, but there is a perennial war and chaos, and there is not much accumulation.

What these two can get hold of, in fact, is only the land of Vietnam.

In addition to showing loyalty to the Zhou Lang regime, the Tay Son Dynasty also wanted to ask the Great Zhou to send troops to support, but the Nguyen clan did not have this request, he was already in sight of victory, and he did not want to have another competitor, he just hoped to be canonized and make him the rightful king of Vietnam.

Zhou Lang communicated with the envoys on both sides, telling the Tay Son Dynasty that it was okay to support, let him accept the land, give the title of Prince Nguyen Quang Truong, hereditary replacement, and the other courtiers would remain unchanged and continue to be officials in Vietnam, and then the Great Zhou army would enter Vietnam to protect them.

But the envoys of the Xishan Dynasty refused, they did not want to hand over the land to the Great Zhou, and were willing to be vassal states, rather than being directly vassals.

The envoy sent by the Nguyen Dynasty was called Zheng Huai Duc, a Vietnamese overseas Chinese, and in the process of developing the Mekong Delta, the Chinese and overseas Chinese contributed a lot, and many people moved their families to where in the late Ming Dynasty, and the Zheng Huai Duc family was also like this.

Because he did not agree with the Xishan Dynasty, Zheng Huai Duc helped Nguyen Phuc Anh gain a firm foothold in Jiading, and has been acting as Nguyen Phuc Anh's envoy, helping him contact foreign countries, and he asked for reinforcements from Siam.

But this time I came not for reinforcements, but for canonization, and brought three people at the same time.

The three big pirates, Mo Guanfu, Liang Wengeng, and Fan Wencai, were recruited by the Xishan Dynasty and attracted by the official positions of the Xishan Dynasty.

Zheng Huaide accused the Xishan Dynasty of colluding with pirates and harming China, hoping that the Great Zhou could expel the envoys of the Xishan Dynasty, the Ruan Dynasty has always admired the Central Plains, and the Great Zhou Dynasty has expelled Hu Lu, as the Central Plains is orthodox, and the Ruan Dynasty is willing to pay tribute every year and come to the Dynasty every year.

Zhou Lang expressed his anger, pretending not to know that the Xishan Dynasty had been supporting the pirates, and immediately threatened to conquer the Xishan Dynasty in the south, and was willing to destroy the dynasty together with the Ruan Dynasty.

Zheng Huaide saw that the strength was used too violently, which made the Chinese emperor angry, once the other side raised troops, I am afraid that the land of northern Vietnam will not exist, and the Ruan family's achievements in unifying Vietnam will be reduced to ashes.

He immediately said that Ruan Fuying would punish the thieves for the country, and did not allow the country to raise troops, and suggested that the country should destroy the Hulu first, the western mountain thieves were just a small trouble, and the Ruan Dynasty should share the worries for the country.

Zhou Lang was noncommittal, and said forcefully that he would not be angry if he did not destroy this dynasty. Then he sent Zheng Huaide.

After Zheng Huaide went out, he immediately wrote a letter to inform Ruan Phuc Anh that he wanted Ruan Phuc Anh to send troops as soon as possible, and that the great powers of the Central Plains would raise troops, and if it was too late, the land of the northern part of Vietnam would not be owned by the Ruan family, and then let his relatives rush back to Jiading by boat as soon as possible.

But it was too late, his speed was not as fast as Zhou Lang, Zhou Lang had already written an order, and with enough evidence of the Xishan Dynasty's collusion with pirates sent by Zheng Huaide, he had a reason to raise an army to fight.

This order was transmitted to Guangxi by horse, and it could be reached within ten days, twice as fast as taking a ship.

Therefore, when Zheng Huaide's ship returned to Jiading, the Guangxi army had already begun to mobilize, there were no main soldiers, and there were some auxiliaries, and a group of local auxiliaries were recruited to suppress all kinds of bandits in Guangxi, many of whom were members of the Heaven and Earth Society, who had crossed China and Vietnam, and still had a close relationship with the Xishan Dynasty.

In addition, the army of Yunnan should also be mobilized, Yunnan and Guizhou provinces were incorporated into the territory after Fugang's surrender, and the army here is still the Qing army in the past, which is basically a green battalion, and more than 3,000 people of the Eight Banners Army were disarmed by Fugang.

Now these green battalions are ordered to enter Vietnam along the Yuan River, receive the cities along the way, publish a list to announce the people, and raise troops to recruit the country, because the Xishan Dynasty did not respect the king, colluded with the Haikou, and caused chaos in the sea frontier.

Zhou Lang really has no soldiers available, otherwise he will never dare to use these green battalions with unclean hands and feet, these people will definitely loot, and when the time comes, it will cause too many local revolts and arouse the anti-aggression spirit of the Vietnamese, then it will be bad, Zhou Lang does not want to be dragged into the quagmire of the Vietnamese People's War.

Because it was a bottomless pit, once the Mongols wanted to annex Vietnam, but they didn't succeed, the Ming Dynasty wanted to annex Vietnam, but they still didn't succeed, and later the Americans also fought Vietnam, but they didn't succeed either.

Therefore, we can only be gentle, not forced. It was necessary to rely on local forces to rule Vietnam, to rule Vietnam with Vietnamese people, and the French did just that, propping up puppets, and then slowly annexing the whole of Vietnam.

Now Zhou Lang needs an obedient puppet.