Liu Bang (256BC-195BC) took the title of Han Gaozu, the first emperor of Han Dynasty (202BC-220AD), when he ascended the throne after defeating Xiang Yu in 202BC. That was right after the brief Qin Dynasty, which had imposed a centralized government on China. But the new nation was no match for the fierce Huns, who had constantly invaded its northern borders. Early Han administrators had no choice but sued for peace, and sent Chinese princesses north as Hun nobles' brides.
By 140 BC, under Liu Che (156BC-87BC), the emperor Han Wudi brought war home to the Huns. He also had several parts of the Great Wall built.
Han Wudi ordered a construction project of the Great Wall in 127 BC. This resulted in rebuilding an older part of the Wall and an extension of territories to present day Mount Yinshan of Inner Mongolia.
Huo Qubing, Emperor Han Wudi's general pushed the Huns back and in 121 BC he secured the Hexi Corridor, the passage to the Western Region. A subsequent Hexi wall construction from present day Yongdeng County to Jiuquan City in Gansu Province had severed contacts between Huns and their allies the Qiang People. The newer wall had joined the eastern terminus of an older network of walls.
Forts dotted the distance between Jiuquan City and Yumenguan Pass of Gansu Province that were also the form of the Great Wall. These were measures against Hun warlords around 110 BC. Around 101 BC Chinese workers built the section from Yumenguan Pass to Luobu Po of Xinjiang Ugyur Autonomous Region. Altogether Han Wudi had built a thousand kilometers (621 miles) of defense wall over twenty years to secure the passage to the Western Region. The Huns power later was in decline and consequently less wall-building activity came about this side of the border.
During the period of Eastern Han, after years of civil wars, Liu Xiu (6BC-57AD), the emperor Guang Wudi could put up only weak resistance to northern invaders. In around 39 AD he gave order to his general Ma Cheng to build four boundary walls to contain the damage. The boundary walls ran 1) from Lishi County of Shanxi Province to southeast of Xianyang City of Shaanxi Province; 2) between Gaoling County of Shaanxi and Anyi County of Shanxi; 3) from Taiyuan City of Shanxi to Jingxing County of Hebei Province; and 4) from Dingxian County of Hebei to Linhang County of Henan Province.
The walls offered some protection to Luoyang, the capital of Eastern Han. Afterwards in-fighting divided the Huns into the North and South. The North Huns were driven off by Han. The more friendly South Huns co-existed with the Han Dynasty and there was no need to build more walls.
