The military history of the Three Kingdoms period encompasses roughly a century's worth of prolonged warfare and disorder in Chinese history. After the assassination of General-in-chief He Jin in September 189, the administrative structures of the Han government became increasingly irrelevant. By the time of death of Cao Cao, the most successful warlord of North China, in 220, the Han empire was divided between the three rival states of Cao Wei, Shu Han and Eastern Wu. Due to the ensuing turmoil, the competing powers of the Three Kingdoms era found no shortage of willing recruits for their armies, although press-ganging as well as forcible enlistment of prisoners from defeated armies still occurred. Following four centuries of rule under the Han dynasty, the Three Kingdoms brought about a new era of conflict in China that shifted institutions in favor of a more permanent and selective system of military recruitment. This ultimately included the creation of a hereditary military class as well as increasing reliance on non-Chinese cavalry forces and the end of universal conscription. Organization Recruitment and organization As the Han dynasty fell into disarray after the Yellow Turban Rebellion, its system of conscription and checks on military leadership broke down, giving local leaders the autonomy to recruit their own personal armies. At the heart of each army was a group of trusted Companions (親近 qinjin) consisting of family members, close friends and clansmen hired by whatever means was available to their lord. Cao Cao's earliest commanders who formed the nucleus of his army were all clansmen (Cao Xiu, Cao Zhen, Cao Chun). There was no need for conscription as the conflicts of the late Han dynasty created willing recruits who sought protection under a strong army. This type of soldier, characterized by a lack of loyalty to state or nation, primarily concerned with survival, made up the majority of the army outside of the leader's close following. Due to the lack of loyalty among common troops, acts of heroism and courage were particularly emphasized among commanders who were expected to lead from the front. A typical example of this type of commander would be Dian Wei, a former local bully noted for his great strength, appetite, and his choice of weaponry, two halberds of immense weight, who served under Cao Cao. In 195, he personally led a group of volunteers clad in double armour (兩鎧 liang kai) against Lü Bu's