Students from the Imperial University organized a widespread student protest against the eunuchs of Emperor Huan's court. Huan further alienated the bureaucracy when he initiated grandiose construction projects and hosted thousands of concubines in his harem at a time of economic crisis. Palace eunuchs imprisoned the official Li Ying (李膺) and his associates from the Imperial University on a dubious charge of treason. In 167 AD, the Grand Commandant Dou Wu (d. 168 AD) convinced his son-in-law, Emperor Huan, to release them. However the emperor permanently barred Li Ying and his associates from serving in office, marking the beginning of the Partisan Prohibitions.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): When did Dou Wu die?
168 AD