u , ▁he ▁took ▁Y uan ▁X i ' s ▁wid ow , ▁Lady ▁Z hen , ▁as ▁a ▁conc ub ine , ▁but ▁in ▁ 2 2 1 ▁Lady ▁Z hen ▁died ▁and ▁Gu o ▁N ü w ang ▁became ▁em press . ▁ ▁On ▁ 2 5 ▁November ▁ 2 2 0 , ▁C ao ▁Pi ▁forced ▁Emperor ▁X ian , ▁the ▁last ▁r uler ▁of ▁the ▁Eastern ▁Han ▁dynast y , ▁to ▁ab d icate ▁in ▁his ▁favour , ▁after ▁which ▁on ▁ 1 1 ▁December ▁ 2 2 0 ▁he ▁proc laimed ▁himself ▁em peror ▁and ▁established ▁the ▁state ▁of ▁C ao ▁Wei . ▁C ao ▁Pi ▁continued ▁the ▁wars ▁against ▁the ▁states ▁of ▁Sh u ▁Han ▁and ▁Eastern ▁Wu , ▁founded ▁by ▁his ▁father ' s ▁riv als ▁Li u ▁Bei ▁and ▁Sun ▁Qu an ▁respectively , ▁but ▁did ▁not ▁make ▁significant ▁territorial ▁gain ▁in ▁the ▁batt les . ▁Un like ▁his ▁father , ▁C ao ▁Pi ▁concentr ated ▁most ▁of ▁his ▁efforts ▁on ▁internal ▁administration ▁rather ▁than ▁on ▁w aging ▁wars ▁against ▁his ▁riv als . ▁During ▁his ▁reign , ▁he ▁formally ▁established ▁Chen ▁Q un ' s ▁nine - rank ▁system ▁as ▁the ▁base ▁for ▁civil ▁service ▁nom ination , ▁which ▁drew ▁many ▁tal ents ▁into ▁his ▁government . ▁On ▁the ▁other ▁hand , ▁he ▁dr ast ically ▁reduced ▁the ▁power ▁of ▁princes , ▁stri pping ▁off ▁their ▁power ▁to ▁opp ose ▁him , ▁but ▁at ▁the ▁same ▁time , ▁rendering ▁them ▁unable ▁to ▁assist ▁the