You might want to read this response by u/aniMayor on the personal bodyguard of Chinese generals from the Three Kingdoms period:
It's lengthy, but u/aniMayor does a wonderful job of describing the elite personal force that generals or other high-ranking officers took with them to battle. More than just protecting their master, this force of veteran soldiers are counted on to cut through enemy formations, especially as most soldiers they face will likely be less well equipped and less well trained. Commanders not only participated in battle for a morale benefit, but also because they led strong units that had pivotal roles in combat.
Follow up. Kings and Emperors are more than not depicted as very competent fighters. Usually if they are defeated in combat it is because they lack the agility and athleticism due to age. How common was it for a ruler to be the best or highly competent in battle? Or was it just a case that they should be because they would have had access to best training and weapons?
As a follow up, how often did they actually lead the charge ? Are situations as shown in movies true or are they a bit of an exaggeration ?