Wuhuan had become somewhat of a dual vassal to both the Han and the Xiongnu during the late Han Dynasty, and, under a policy in effect since 121 BCE, is supposed to pay Xiongnu tributes in textile and leather.

Should Wuhuan fail to pay the tributes, Xiongnu forces kidnap Wuhuan women as hostages.

The first sign of irritation with Wang Mang’s policies had come sometime before 10, by which time the Xin director of Wuhuan affairs had informed the Wuhuan tribes not to pay further tribute to Xiongnu.

In response, the Xiongnu mount a punitive military action against Wuhuan, taking hostage about one thousand women and children.

At Wang Mang's orders, the Xiongnu are later forced to return the Wuhuan hostages.

The usurper Wang Mang sends his ambassadors to the Xiongnu in 10 to inform Chanyu Zhi that he has become emperor and that Xin has replaced Han, and requests that the great seal of the chanyu, which the Han had issued, be exchanged for a new seal issued by Xin.

The old seal reads, "the Great Seal of the Chanyu of Xiongnu", while the new seal reads, "the Seal of the Shanyu of Gongnu of Xin", changing the meanings "ferocious vassal" to "respectful vassal", "Chanyu" to "Shanyu", and "seal" to "badge", implying that the Xiongnu polity, which the Han had treated with some ambiguity about whether it was a vassal, is clearly a vassal of Xin.

Without examining the new seal, Chanyu Zhi agrees to the exchange.

The ambassadors, apprehensive that the Chanyu, once he realizes what had happened, would demand the old seal back, destroy the old seal.

Indeed, the next day, the Chanyu realizes that the seal text had changed, and requests that the old seal be returned, but upon being informed that the old seal had been destroyed (which the ambassadors claimed falsely to be an act of the gods), acquiesces.

Chanyu Zhi, however, begins to prepare for confrontation with the Xin dynasty.

He builds defensive bulwarks some distance from the Xin outpost of Shuofang (roughly modern Ordos, Inner Mongolia).

He also begins to accept the Xiyu ("Western Yu", in modern Xinjiang and former Soviet central Asia) kingdoms' pledges of allegiance, which were banned previously by Wang.

Wang, irritated with Chanyu Zhi, declares war against Xiongnu.

The strategy that he sets out is to divide the Xin forces into twelve armies to divide and conquer Xiongnu.

Under this scenario, Chanyu Zhi would be attacked and forced to retreat to the Dingling tribes (around Lake Baikal), and Xiongnu would be divided into fifteen small kingdoms to be ruled by fifteen descendants of Chanyu Huhanye, who had first established friendly relations with Han.

Under this plan, three hundred thousand men would be gathered (and would attack at the same time).

Wang does not follow his generals' recommendations to start the campaign as soon as a critical mass of men is gathered, but wants to attack with overwhelming force.

This causes the border regions to become strained with accommodating the men who had already arrived for years, while fruitlessly waiting for the full support of three hundred thousand to be gathered.

Wang had requisitioned the forces of Korean tribes within the borders of Xin-controlled territory when he began his campaign against Xiongnu.

The Korean tribes had refused, and marched beyond the borders; the army that Wang sent against them are defeated.

The general Wang had sent, Yan You, had used humble words to deceive their leader, Zou, who carries the title the Marquess of Gaojuli, (Goguryeo, but apparently having no direct connection with the contemporary Kingdom of Goguryeo), into a meeting with him, and then killing Zou by surprise.

Wang then changes Gaojuli to the derogatory term "Xiajuli" (gao means "high", while xia means "low"), which further enrages the Koreans, causing them to attack the Xin northeastern regions with greater ferocity.

Powerful Chinese landlords hostile to Wang Mang’s reforms support the angry and confused peasantry against the new emperor.

Eventually, with resistance to his land redistribution and anti-slavery policies, Wang is forced to repeal both in 12.

One of the local commanders kidnaps one of Chanyu Zhi's brothers, Xian, the Prince of Zuoliwu, and his sons Deng and Zhu, by trickery in the first stage of Wang Mang’s plan.

Xian and Zhu are made Chanyus—to be two of the fifteen.

An enraged Chanyu Zhi initiates massive attacks against Xin border regions, causing the border regions much distress and loss in economic and human terms.

Eventually, Xian escapes back to Xiongnu, but his sons are kept as hostages.

After Zhu dies, Deng succeeds him.

However, in 12, after hearing reports that Xian's other son Jiao had been a successful Xiongnu strategist in military actions, Wang, in anger, executes Deng and his attendants.

Chanyu Zhi dies later in 13, and the powerful official Xubu Dang and his wife Yun, the Princess Yimuo (the daughter of Chanyu Huhanye and Wang Zhaojun), who advocates peaceful relations with the Xin dynasty and who are also friendly with Xian, support Xian as the new Chanyu, but even though Xian is unaware that Wang Mang had executed his son Deng, their friendly relations do not return.

There is a temporary détente in 14, when Xian returns Xin defectors Chen Liang and Zhong Dai who, as junior army officers in Xiyu, had killed their superiors and surrendered to the Xiongnu (perhaps seeking to have the Xiongnu help them reestablish Han rule) so that Wang could execute them.

In reciprocation, Wang recalls the forces to the northern regions that had been intended to attack Xiongnu (but have never received the full support that Wang had envisioned).

However, after Chanyu Xian discovers, late in 14, that Deng had been executed, he resumes raids against the border regions but maintains a façade of peaceful intention.

A major problem plaguing Wang Mang's administration, in addition to the internal wars waged by the Xin dynasty, is his strong commitment in determining the ancient governmental structure, believing that once things were restored to Zhou Dynasty standards, the government would be efficient.

He and his officials have thus spent inordinate amounts of time carrying out research of ancient legends, leaving important affairs of the state undecided.

For years, a large number of counties have lacked magistrates.

The local officials, without supervision, have become highly corrupt and oppressive of the populace.

Because of the way Wang had come to power, he has become suspicious of allowing his subordinates to accrue too much power.

Wang therefore makes all important decisions by himself and does not delegate, leaving him highly fatigued and many decisions unmade.

Further, he has entrusted eunuchs to screen the reports from local governments for him, but those eunuchs decide to relay or not relay those reports based on their own personal likes and dislikes, and many important petitions go unanswered.

An even more serious problem is that the officials lack salaries.

The Han dynasty had a well-defined system of official salaries, but when Wang became emperor, he had ordered that the salary system be overhauled and recalibrated; however because the creation of a new system has taken years, the officials have in the meantime gone without salaries.

In response, they have become corrupt in demanding bribes from the people, causing the people great distress.

Another economic change instituted by Wang Mang—a fairly disastrous one—has been to issue twenty-eight types of coins, made of gold, silver, tortoise shells, sea shells, and copper.

Because there are so many kinds of coins (in contrast to the one kind used under the Han dynasty), people have become unable to recognize the kinds of coins as genuine or as counterfeit, and the money-based economy has come to a halt.

Wang is forced eventually to abolish all but two kinds of coins—the small coin that has the same value of a Han coin, and the large coin that has the value of fifty small coins.

However, the people, despite fairly severe penalties, have lost faith in the Xin coins, and continue to use Han coins in an underground trade economy.

In an attempt to refill the depleted imperial coffers in 17, Wang institutes six monopolies—of liquor, salt, iron, coinage, forestry, and fishing.

However, because of rampant corruption, the imperial treasury receives only limited benefit, while the people are greatly burdened.