On the wheels of that thread being a rousing success I feel I must provide additional context.
In late IInd century AD/CE, China was ruled by the Han dynasty who until then had a decent run of 4 centuries or so. However the Imperial court was plagued by intrigue (squarely blamed on eunuchs), weak rulers and internal turmoil. As it generally happens, a combination of bad harvests & poor governance finally erupted in a massive revolt by commoners dubbed the Yellow Turbans/Scarfs rebellion which maybe left millions dead all told and said. To quell the uprising, armies were raised everywhere by local dignitaries. It didn't slow down intrigue in the capital and soon there was a succession crisis involving 2 heirs that were still children / young teens... You now have a bunch of warlords with huge armies in a power vacuum and the time is ripe to make a play for ABSOLUTE POWER. Ultimately the power struggle will filter down to three competing kingdoms / proclaimed dynasties (Wei, Shu, Wu) locked in a long stalemate but we're not yet at that point in our story.
The most important early players are :
- Liu Bei, a distant relative of the imperial family living a simple life supporting his mother until he levies an army to fight the Yellow Turbans alongside Zhang Fei and Guan Yu who become his sworn brothers.
- Cao Cao, a smart man reputed to be a great strategist (he supposedly annotated the Art of War by Sun Tzu) and scholar (poet, calligrapher) who makes the right moves early on to become the "guardian" of the capitol and the emperor, giving him that thick veneer of legitimacy and establish the Wei region.
- Lu Bu, the mightiest warrior of the era but all that min/maxing left him with a dismal LOYALTY stat that is about to bite him in the ass for good very soon.
The Romance... is often considered to be pro-Shu hence pro Liu Bei, with Cao Cao being elevated to the main antagonist.
In actuality, neither Wei, Wu or Shu will reunite China. The honor goes to rebellious officials from Wei forming the Jin dynasty. The pro Shu bias a millenia down the line is chalked up to a few explanations, from using Shu sources as the most primary or XIVth century political considerations colouring what was highlighted in the tale.