Quick questions on Emperor Wu of Han: expansion and reforms 141-87 BC: HSC Ancient History

Since Gaozu's near-capture at Baideng in 200 BC, the Han had contained the Xiongnu steppe confederation through heqin ("harmonious kinship"): marrying Han princesses to the chanyu and sending annual gifts of silk, grain and wine to buy peace. Emperor Wu ended this appeasement. In 133 BC he laid the Mayi ambush, a plan to lure the chanyu's army into a trap near the frontier town of Mayi; the trap failed, but it broke the peace and opened decades of open war.

The Xiongnu wars opened the way west. Huo Qubing's campaigns of 121 BC cleared the Xiongnu from the Hexi (Gansu) corridor, the narrow band of oases running north-west from the Han heartland, and over the following decades the Han planted the four Hexi commanderies (Wuwei, Zhangye, Jiuquan and Dunhuang) to hold it. This corridor became the gateway to the Western Regions of Central Asia.

Emperor Wu also gave the state an official ideology. His court scholar Dong Zhongshu urged, in memorials answering the emperor's policy questions around 134 BC, that the competing "hundred schools" of philosophy be set aside and Confucian classics alone made the foundation of official learning, supplying the throne with a single moral language of the Mandate of Heaven and hierarchical loyalty. Wu acted on the advice in stages: in 136 BC he appointed Erudites (boshi) dedicated to the Five Classics; in 124 BC he founded the Taixue (Imperial University) at Chang'an, beginning with about 50 students; and the xiaolian ("filial and incorrupt") recommendation system tied office-holding to reputation and, increasingly, Confucian learning.