Complex sentence: He joined Cao Cao since the early years of the civil war that led to the collapse of the Han Dynasty and fought in many of the campaigns that established the warlord's position as a central figure of the Three Kingdoms.
Split into simpler sentences: He joined Cao Cao in the early years of the civil wars that led to the collapse of the Han Dynasty. He fought in many of the campaigns that established the warlord's position as a central figure of the Three Kingdoms.