Ming Great Wall in the context of "Mu Us Desert"

Shaanxi is a province in north Northwestern China bordering the province-level divisions of Inner Mongolia to the north; Shanxi and Henan to the east; Hubei, Chongqing, and Sichuan to the south; and Gansu and Ningxia to the west. Shaanxi covers an area of over 205,000 km (79,000 sq mi) with about 37 million people, the 16th-largest in China. Xi'an, which includes the sites of the former capitals Fenghao and Chang'an – is the provincial capital and largest city in Northwest China and also one of the oldest cities in China. It is also the oldest of the Four Ancient Capitals, being the capital for the Western Zhou, Western Han, Jin, Sui and Tang dynasties. Xianyang, which served as the capital of the Qin dynasty (221–206 BC), is just north across the Wei River. The other prefecture-level cities into which the province is divided are Ankang, Baoji, Hanzhong, Shangluo, Tongchuan, Weinan, Yan'an and Yulin.

The province is geographically divided into three parts, namely Northern (or "Shaanbei"), Central ("Shaanzhong") and Southern Shaanxi (or "Shaannan"). Northern Shaanxi makes up the southeastern portion of the Ordos Basin and mainly comprises the two prefectural cities of Yulin and Yan'an on the northern Loess Plateau, demarcated from the Ordos Desert and the grasslands of Inner Mongolia's Ordos City by the Ming Great Wall. Central Shaanxi is also known as the Guanzhong region, and comprises the drainage basin of lower Wei River east of Mount Liupan and north of the Qinling Mountains, where the majority of Shaanxi's population reside. Southern Shaanxi comprises the three prefectural cities in the edge of the historical Bashu region south of the Qinling Mountains and includes the three mountainous cities of Hanzhong, Ankang and Shangluo.

The Shanhai Pass (simplified Chinese: 山海关; traditional Chinese: 山海關; pinyin: Shānhǎi Guān; lit. 'Mountain Sea Pass') is a major fortified gateway at the eastern end of the Great Wall of China and one of its most crucial fortifications, as the pass commands the narrowest choke point in the strategic Liaoxi Corridor, an elongated coastal plain between the Yan Mountains foothills and the Bohai Sea, which is the only easily traversable landway between North and Northeast China. It is located in present-day Shanhaiguan District, Qinhuangdao, Hebei province, on the east bank of the Shi River, with defensive walls stretching from the Yan Mountains all the way to the shores of the Liaodong Bay.

Throughout Chinese history, garrisons around the pass served as frontline defensive outposts against raids and incursions into the North China Plain by various non-Sinitic ethnic groups from the Northeast (also known as Manchuria since the 19th century), including the Dongyi, Donghu (Xianbei and Wuhuan), Khitan and Jurchen (Manchus). The current Shanhai Pass was built during the early Ming dynasty as the easternmost fortification of the Ming Great Wall, and was extensively reinforced after Yongle Emperor moved the capital from Nanjing to Beijing following the Jingnan campaign, making it the most important defensive barrier in all of China, as it shielded the heartland region around the imperial capital. The pass' strategic location dictated that without mounting a costly direct siege, the only way an invading army can get past the pass' defense was to circumvent it around the north through a few treacherously narrow mountain passes deep within the Yan Mountains, which would make it very difficult to maintain supply lines and thus any sizeable invasions. This defensive significance therefore earned the pass the famous nickname "Greatest Pass Under Heaven" (天下第一关).

Northern Shaanxi or Shaanbei (陕北) is the northern portion of China's Shaanxi province. More specifically, it refers to the region north of the Huanglong Mountain and the Meridian Ridge (the so-called "Guanzhong north mountains") within the province. Being both a geographic area as well as a cultural area, it makes up the southeastern portion of the Ordos Basin and forms the northern part of the Loess Plateau. The region includes two prefecture-level cities: Yulin, which is known for the Ming Great Wall traversing through its northern part; and Yan'an, which is known for being the birthplace of the Chinese Communist Revolution.

The Yongli Emperor (1623–1662), personal name Zhu Youlang, was the fourth and last emperor of the Southern Ming dynasty, reigning in turbulent times when the former Ming dynasty was overthrown and the Manchu-led Qing dynasty progressively conquered the entire China proper. He led the remnants of the Ming loyalists with the assistance of peasant armies to resist the Qing forces in southwestern China, but he was then forced to exile to Toungoo Burma and eventually captured and executed by Wu Sangui in 1662. His era name "Yongli" means "perpetual calendar".

Zhu Youlang was the son of Zhu Changying (朱常瀛), the seventh son of the Wanli Emperor, and Empress Dowager Ma. He inherited the title Prince of Gui (桂王) from his brother and lived an obscure life as a minor member of the Ming imperial family until the rebellions of peasant armies, which resulted to the fall of the imperial capital, Beijing, and the suicide of the last Ming emperor, Chongzhen, after the peasant rebel leader Li Zicheng captured Beijing in 1644. The true beneficiaries of the collapse of the Ming were the Qing dynasty, ruled by the emerging nation Manchus from Manchuria. After mass defection from Ming remnants, including a former Ming general, Wu Sangui, who allowed the Qing forces to pass the Ming Great Wall against Li Zicheng. The Qing forces defeated the peasant armies and rapidly expanded to northern China, the Lower Yangtze valley, and Central China. The Ming loyalists continued to resist in southern China, with several former Ming royal members regrouping in the south in attempt to re-establish the Ming governance, but all failed before the rapid Manchu military advance. Youlang ascended the throne in Zhaoqing as the fourth Southern Ming emperor in November 1646.

Hetao (Chinese: 河套; pinyin: Hétào; lit. 'river loop') is a C-shaped region in northwestern China consisting of a collection of flood plains stretching from the banks of the northern half of the Ordos Loop, a large northerly rectangular bend of the Yellow River, that forms the river's entire middle section. The region makes up the northern margin of the Ordos Basin, bounded in the west by the Helan Mountains, the north by the Yin Mountains, the east by the northern portion of Lüliang Mountains, and the south by the Ordos Desert and the Loess Plateau (separated by the course of the Ming Great Wall).

The Hetao region is divided into two main sections — the "West Loop" (Chinese: 西套; pinyin: Xītào) in Ningxia, and the "East Loop" (Chinese: 东套; pinyin: Dōngtào) in Inner Mongolia. The west section includes the alluvial Yinchuan Plain (Chinese: 银川平原, a.k.a. Ningxia Plain) around Shizuishan, Yinchuan, and Wuzhong, and the Weining Plain (Chinese: 卫宁平原) around Zhongwei. The east section is further divided into two parts — the western "Back Loop" (Chinese: 后套; pinyin: Hòutào), which includes the Bayannur Plain (Chinese: 巴彦淖尔平原) around Bayannur and Wuhai; and the eastern "Front Loop" Chinese: 前套; pinyin: Qiántào), which includes the Tumochuan Plain (Chinese: 土默川平原) around Baotou and Hohhot.