Question: Whose threat was partly responsible for the Chinese expansion into the Ordos region?
About the article "Archery", section "Mounted archery".

Candidate passages:
Central Asian tribesmen (after the domestication of the horse) and American Plains Indians (after gaining access to horses) became extremely adept at archery on horseback.
Lightly armoured, but highly mobile archers were excellently suited to warfare in the Central Asian steppes, and they formed a large part of armies that repeatedly conquered large areas of Eurasia.
Shorter bows are more suited to use on horseback, and the composite bow enabled mounted archers to use powerful weapons.
Empires throughout the Eurasian landmass often strongly associated their respective "barbarian" counterparts with the usage of the bow and arrow, to the point where powerful states like the Han Dynasty referred to their neighbours, the Xiong-nu, as "Those Who Draw the Bow" For example, Xiong-nu mounted bowmen made them more than a match for the Han military, and their threat was at least partially responsible for Chinese expansion into the Ordos region, to create a stronger, more powerful buffer zone against them.
It is possible that "barbarian" peoples were responsible for introducing archery or certain types of bows to their "civilized" counterparts—the Xiong-nu and the Han being one example.
Similarly, short bows seem to have been introduced to Japan by northeast Asian groups.
In 215 BCE, Qin Shi Huangdi ordered General Meng Tian to set out against the Xiongnu tribes, situated in the Ordos region, and establish a frontier region at the Ordos Loop.
Believing that the Xiongnu were a possible threat, the emperor launched a preemptive strike against the Xiongnu with the intention to expand his empire.
In 215 BCE, General Meng Tian succeeded in defeating the Xiongnu and driving them from the Ordos region, then he seized their homeland.
After the catastrophic defeat at the hands of General Meng Tian, the Xiongnu leader Touman was forced to flee far into the Mongolian Plateau.
As a result of the northward expansion, the threat that the Qin empire posed to the Xiongnu ultimately led to the reorganization of the many tribes into a confederacy.
General Meng Tian was instructed to secure the frontier with a line of fortifications, which would become known as the Great Wall of China.
Fusu (Prince of Qin) and General Meng Tian were stationed at a garrison in Suide and soon began with the construction of the walled defenses, which would be connected with the old walls from the Qin, Yan, and Zhao states.
The Qin walls ran from Liaodong to Lintao, thus enclosing the conquered Ordos region. 
The Ordos (Mongolian Cyrillic: Ордос) are a Mongol subgroup that live in Uushin district, Inner Mongolia.
Ordos literally means plural of Ordo.
The Three Tribes of Uriyangkhaid, Tümed in north Shanxi, Ordos Mongols in Ordos and north of Shensi extended southward beyond the Ming defense zone in the 14-15th centuries.
Since 1510, the Ordos were ruled by descendants of Batumongke Dayan Khan.
The Ordos Mongols believe that they have been responsible for the shrine of Genghis Khan since their inception.
However, the modern place where mausoleum of Genghis Khan located is inhabited by the Darkhads because the Ordos Mongols were forced to be resettled outside Ordos grasslands.
Traditionally, Ordos territory is divided into 7 banners.
Their number reached 64,000 in 1950 and a possible current estimate of the Ordos people might be less than 100,000. 
However, while the empire at times was extended to the north, the Qin could rarely hold on to the land for long.
The tribes of these locations, collectively called the Hu by the Qin, were free from Chinese rule during the majority of the dynasty.
Prohibited from trading with Qin dynasty peasants, the Xiongnu tribe living in the Ordos region in northwest China often raided them instead, prompting the Qin to retaliate.
After a military campaign led by General Meng Tian, the region was conquered in 215 BC and agriculture was established; the peasants, however, were discontented and later revolted.
The succeeding Han dynasty also expanded into the Ordos due to overpopulation, but depleted their resources in the process.
Owen Lattimore said of both dynasties' attempts to conquer the Ordos, "conquest and expansion were illusory.
There was no kind of success that did not create its own reaction."
Indeed, this was true of the dynasty's borders in multiple directions; modern Xinjiang, Tibet, Manchuria, Inner Mongolia, and regions to the southeast were foreign to the Qin, and even areas over which they had military control were culturally distinct. 
During the Warring States period, the Qin, Zhao, and Yan states conquered various nomadic territories inhabited by the Xiongnu and other Hu peoples.
They reinforced their new frontiers with elongated wall fortifications.
By 221 BC, the Qin ended the chaotic Eastern Zhou period by conquering all other states and unifying the entire nation.
In 215 BC, Qin Shi Huang ordered General Meng Tian to set out against the Xiongnu tribes, situated in the Ordos region, and establish a frontier region at the Ordos Loop.
Believing that the Xiongnu were a possible threat, the emperor launched a pre-emptive strike against the Xiongnu with the intention to expand his empire.
Later that year (215 BC), General Meng Tian succeeded in defeating the Xiongnu and driving them from the Ordos region, seizing their territory as result.
After the catastrophic defeat at the hands of Meng, Touman Chanyu and his followers fled far into the Mongolian Plateau.
Fusu (Prince of Qin) and General Meng Tian were stationed at a garrison in Suide and soon began with the construction of the walled defenses, connecting it with the old walls built by Qin, Yan and Zhao states.
The fortified walls ran from Liaodong to Lintao, thus enclosing the conquered Ordos region, safeguarding the Qin empire against the Xiongnu and other northern nomadic people.
Due to the northward expansion, the threat that the Qin empire posed to the Xiongnu ultimately led to the state formation of the many tribes towards a confederacy.
However, after the sudden death of Qin Shi Huang, the ensuing political corruption and chaos during the short reign of Qin Er Shi would lead to various anti-Qin rebellions, eventually bring about the collapse of the Qin Dynasty.
A massive civil war then erupted between various reinstated states, with Liu Bang eventually victorious to establish the Han Dynasty.
During the transitional years between Qin and Han, while the Chinese were mainly focused towards the interior of their nation, the Xiongnu took the opportunity to retake the territory north of the wall.
The Xiongnu frequently led incursions to the Han frontier and had considerable political influence over the border regions.
In response, Emperor Gaozu led a Han army against the Xiongnu in 200 BC, pursuing them as far as Pingcheng (present-day Datong, Shanxi) before being ambushed by Modu Chanyu's cavalry.
His encampment was encircled by the Xiongnu, but Emperor Gaozu escaped after seven days.
After realizing that a military solution was not feasible for the time being, Emperor Gaozu sent Liu Jing to negotiate peace with Modu Chanyu.
In 198 BC, a marriage alliance was concluded between the Han and the Xiongnu, but this proved far from effective as the incursions in the frontier regions continued.