Huai River in the context of "Hefei"

The Qinling–Huaihe Line (Chinese: 秦岭淮河线; pinyin: Qínlǐng Huáihé Xiàn) is a reference line used by geographers to distinguish between northern and southern China, corresponding roughly to the 33rd parallel. Qinling refers to the Qin Mountains, and Huaihe refers to the Huai River. Running from Qin Mountain in the west to Huai River in the east, it divides eastern China into northern and southern regions that differ from each other in climate, culture, lifestyle, and cuisine.

Regions north of the Line tend to be temperate or continental, with snow being a regular feature in winter. Regions south of the Line tend to be subtropical or tropical. In general, the southern region is hotter, wetter, and much more hilly than the northern region.

Lower Yangtze Mandarin (traditional Chinese: 下江官話; simplified Chinese: 下江官话; pinyin: Xiàjiāng Guānhuà) is one of the most divergent and least mutually-intelligible of the Mandarin language varieties, as it neighbours the Wu, Hui, and Gan groups of Sinitic languages. It is also known as Jiang–Huai Mandarin (traditional Chinese: 江淮官話; simplified Chinese: 江淮官话; pinyin: Jiānghuái Guānhuà), named after the Yangtze (Jiang) and Huai Rivers. Lower Yangtze is distinguished from most other Mandarin varieties by the retention of a final glottal stop in words that ended in a stop consonant in Middle Chinese.

During the Ming dynasty and early Qing dynasty, the lingua franca of administration was based on Lower Yangtze Mandarin. In the 19th century the base shifted to the Beijing dialect.

The Grand Canal (Chinese: 大运河; pinyin: Dà yùnhé) is a system of interconnected canals linking various major rivers and lakes in North and East China, serving as an important waterborne transport infrastructure between the north and the south during Medieval and premodern China. It is the longest artificial waterway in the world and a World Heritage Site.

The Grand Canal has undergone several route changes throughout history. Its current main stem, known as the Jing–Hang Grand Canal, is thought to extend for 1,776 km (1,104 mi) linking Beijing in the north to Hangzhou in the south, and is divided into 6 main subsections, with the southernmost sections remaining relatively unchanged over time. The Jiangnan Canal starts from the Qiantang River at Hangzhou's Jianggan District, looping around the east side of Lake Tai through Jiaxing, Suzhou and Wuxi, to the Yangtze at Zhenjiang; the Inner Canal from Yangzhou across the Yangtze from Zhenjiang, going through the Gaoyou Lake to join the Huai River at Huai'an, which for centuries was also its junction with the former course of the Yellow River; the Middle Canal from Huai'an to Luoma Lake at Suqian, then to the Nansi Lakes at Weishan; the Lu Canal from the Nansi Lakes at Jining and into the present course of the Yellow River at Liangshan, splitting off downstream at Liaocheng's Dong'e County before continuing to the Wei at Linqing; the Southern Canal (named for its location within Hebei) from Linqing to the Hai River at Tianjin; and the Northern Canal from Tianjin to Tongzhou on the outskirts of Beijing. As such, it passes through the provinces of Zhejiang, Jiangsu, Shandong, Hebei, and the municipalities of Tianjin and Beijing. In 2014, the Chinese government and UNESCO recognized the Eastern Zhejiang Canal from Hangzhou to Ningbo along the former Tongji and Yongji Canals also as official components of the Grand Canal.

The Dabie Mountains (traditional Chinese: 大別山; simplified Chinese: 大别山; pinyin: Dàbié Shān) are a major mountain range located in central China. Running northwest-to-southeast, they form the main watershed between the Huai and Yangtze rivers. The range also marks the boundary between Hubei Province (near Tingqian town) and its neighbors of Henan (to the north) and Anhui (to the east). During the late 1920s and early 1930s, the Dabie Mountains were a stronghold of the Chinese Communist Party and the location of the Eyuwan Soviet.

The western part of the Dabie Mountains has a low elevation of only 1,000–1,300 feet (300–400 meters), though there are a few peaks rising to 3,000 feet (910 meters). The eastern part is higher, averaging more than 3,300 feet (1,000 meters). The highest peak is Baimajian at 1,777 meters (5,830 feet), with several others topping 5,000 feet (1,500 meters) including the 1,729.13 meters (5,673.0 ft) high Tiantangzhai.

The Huai Army (Chinese: 淮軍; pinyin: Huái jūn), named for the Huai River, was a military force allied with the Qing dynasty raised to contain the Taiping Rebellion in 1862. It was also called the Anhui Army because it was based in Anhui province. It helped to restore the stability of the Qing dynasty. Unlike the traditional Green Standard Army or Eight Banners forces of the Qing, the Huai Army was largely a militia army, based on personal rather than institutional loyalties. It was armed with a mixture of traditional and modern weapons. Li Hongzhang, a commander in the Xiang Army, created the Huai Army in October 1861. It succeeded Zeng Guofan’s Xiang Army. The Huai Army itself was succeeded by the New Army and the Beiyang Army, which were created in the late 19th century, though it continued to exist until the end of the dynasty in 1911.

Emperor Wu of Jin (simplified Chinese: 晋武帝; traditional Chinese: 晉武帝; pinyin: Jìn Wǔ Dì; Wade–Giles: Chin Wu-Ti; 236 – 16 May 290), personal name Sima Yan (Chinese: 司馬炎; pinyin: Sīmǎ Yán), courtesy name Anshi (安世), was a grandson of Sima Yi, nephew of Sima Shi and son of Sima Zhao. He became the first emperor of the Jin dynasty after forcing Cao Huan, last emperor of the state of Cao Wei, to abdicate to him. He reigned from 266 to 290, and after conquering the state of Eastern Wu in 280, was the emperor of a reunified China. Emperor Wu was also known for his extravagance and sensuality, especially after the unification of China; legends boasted of his incredible potency among ten thousand concubines.

Emperor Wu was commonly viewed as generous and kind, but also wasteful. His generosity and kindness undermined his rule, as he became overly tolerant of the noble families' (世族 or 士族, a political/bureaucratic landlord class from Eastern Han to Tang dynasty) corruption and wastefulness, which drained the people's resources. Further, when Emperor Wu established the Jin Dynasty, he was concerned about his regime's stability, and, believing that the predecessor state, Cao Wei, had been doomed by its failures to empower the princes of the imperial clan, he greatly empowered his uncles, his cousins, and his sons with authority, including independent military authority. This ironically led to the destabilization of the Western Jin, as the princes engaged in an internecine struggle known as the War of the Eight Princes soon after his death, and then the "Five Barbarians" uprisings that destroyed the Western Jin and forced its successor, Eastern Jin, to relocate to the region south of the Huai River.