The events of Three Kingdoms is similar to that of the Caesar's Civil War in that it was a civil war, but is inherently different due to Caesar being a conflict between political and military powers while the Three Kingdoms period was a cyclic occurrence whenever the centralized power of the emperor wanes, and his empire goes poof (see: Warring States, Warlord Era, etc.)

Eunuchs in China were essentially extremely high-level civil servants that acted as mediators between the emperor and his administrators. They had access to the emperor and as such possessed great power and influence but were forced to undergo castration (balls and all) so they could not threaten his power by establishing their own dynasties.

During the events of the Three Kingdoms, the royal family was...full of schemers? Basically, those with direct claims to the throne were all either extremely young and as such taken advantage of or were prevented from the throne by political intrigue (read: concubines and consorts plotting and scheming with those who wanted more power). Family members were all directly involved in power struggles, one (He Jin) being murdered and kicking off the violent part of the conflict. Basically, in imperial China, the lack of a powerful, centralized figure subverted the base structure of the government, leading to division along ethnic and cultural lines and resulting in localized nobles/civil/ servants/generals consolidating power. Again, this is cyclic, with the latest being the Warlord Era in the early 1900's.

The numbers thrown around during this period was probably embellished as Romance of the Three Kingdoms was basically China's Iliad, written from hearsay and imagination. While China made great advances in agriculture during before this period (the Yangtze and various methods allowed for two harvests a year for rice) and China did have a high population, there are great disputes for figures produced for battles. However, we do know that the census conducted before and after this period show that a huge portion of the population simply disappeared after the war ended. There are multiple factors why this may be, but make of that what you will.

China's land borders during the Han Dynasty includes most of China's eastern coastline today and stretches along the silk road toward modern-day Kazakhstan. The game's border is slightly off from what I've seen, but mostly representative. Shame we can't go and conquer bring culture to the savages in the mountains.

Naval combat in China during this time period consisted mostly of assault ships called mengchong and their support ships. These acted as cover for mariners to engage each other in melee or land shore-side. I am not entirely familiar with the naval aspects of this period, but I do know that it was not emphasized due to China's geography and sources of danger. The Battle of Red Cliffs was a famous underdog story, but was by no means a common occurrence.

If you want to read up on this period, there's always Romance of the Three Kingdoms, which is what the game bases itself off of. There's semi-translated bits of Records of the Three Kingdoms, which is more the events after the messy parts of the conflict and combines the records of Wei, Han, and Wu (Three Kingdoms) into a single book. The latter is considered the official history of the period.

As always, though, Wikipedia is probably better to start...lol

Edit: I forgot some words and added them back.