Romance of the Three Kingdoms Themes
The Romance of the Three Kingdoms deals with similar themes as many great world epics: the rise and fall of fortunes, and how greed and ambition are fixed parts of human nature.
In the novel as in much of Chinese history, the control of China is not kept within a single royal family line. Instead, the Chinese government is seized by a series of different ruling families who inevitably reign for a few centuries before being overthrown by another ruling family or military faction.
In Chinese culture, this idea is represented by the doctrine of the Mandate of Heaven, which essentially states that if a king is overthrown, then he was not worthy of the throne and it is the will of the gods that the new king/ruling family lord over the country. In The Romance of the Three Kingdoms, this is depicted as a cycle within Chinese history, something tragic and yet never changing in spite of the progress of time.
Concerning itself with the rise and fall of dynasties, The Romance of the Three Kingdoms also deals with human nature, namely human desires for greater power in the social and political spheres. These elements make much of the story tragic in nature as these desires can often lead to great unhappiness and bloodshed between the different families and factions.
Characters' fortunes rise and fall, not just due to the circumstances of the times in which they live, but also due to their own flaws as individuals. For example, Guan Yu's courage proves a double-edged sword, making him arrogant as well as decisive and bold, and this quality, in the right circumstances admirable, leads to his eventual downfall and death. Thus, the story shows how the greater problems of human nature and individual hubris are intertwined.
Another theme might be the necessity of death to establish new life—or in this case, the necessity of the old orders dying out so the kingdom can be revitalized under new leadership.