Ever wonder why mainland France is all of two provinces in Empire? note France proper and Alsace-Lorraine. It's because of the centralizing nature of Louis XIV's government.
In most of the games in the series, when you win the campaign, the ending cutscene will show how you have gloriously crushed your enemies. This is in sharp contrast to the entries that were set during or after the Enlightenment (Empirenote Especially if you are playing as a republic and Fall of the Samurai), in which it is a lot more melancholy, with you general/lord lamenting the human cost of his conquests and telling the citizens to never forget the military's brave sacrifices. This is most likely the result of Deliberate Values Dissonance between the different eras that the entries were set in. Considering that throughout most of history, war is both glorified by the state and that the general public of a nation didn't care much about war as long as it wasn't affecting them (It is highly unlikely that the ancient Romans or the feudal Shoguns cared much for the treatment and suffering of the conquered population). For games set during the Industrial Revolution however, there would have been an intellectual class who realized the terrible reality of war thanks to more widespread education, and it would have affected the ruling class' opinions accordingly one way or the other.
Why does the battle announcer from Rome sound like an inexperienced young man (even though his voice actor is capable of having an older voice as proven in the Scipii campaign intro)? It might be because he's a tribunus laticlavius, a military tribune who serves as second-in-command. Said tribune is a young man from a rich family with no previous military experience whatsoever.
If you win the campaign as a pro-Imperial faction, you have just resurrected the concept for the Emperor's divine right to rule over the country. Which set the stage for the rise of the nationalistic and aggressive Imperial Japan, allowing the military to take over the country in modern times half a century later. Meaning your actions will indirectly lead to horrors such as the Japanese subjugation of Korea and the Second Sino-Japanese War, which ultimately ends with two atomic bombs dropped on the country.
One of the top-tier traits for the Ishin Shishi (imperial political agents) is even called "Arch-imperialist", and its quote is, "Japan has a sacred mission, a destiny!".
If you win the campaign as a pro-Shogunate faction, then you have just prevented Japan's transformation out of the traditional feudal system and the dissolution of the Samurai caste (who are no better than feudal knights), thus saving and preserving an outdated system that is both incredibly violent and oppressive to the majority of the population. By you winning, you have effectively turned the clock back for another two hundred years and stopped the country's modernization right in its tracks.
Not necessarily, considering how the pro-Shogunate side tended to be more accommodating to Westerners. If anything, a victory for that faction would most likely have Japan end up either as a buffer/puppet state between the Western powers or modernize anyway while retaining the pretenses of the old order.
Which leaves us with the Independent/Republic ending. It gives you a small Hope Spot that perhaps you can have a chance to prevent Japan from making all the mistakes that they made in our timeline by transforming the country into a democracy without the need of a devastating world war. However, in the victory cutscene, you were referred to by your general as 'our mighty leader', instead of, say, 'Mr. President' or 'Prime Minister'. Strongly implying that instead of creating a true constitutional democratic state, under your rule the country will become nothing more then another People's Republic of Tyranny.
Regardless of how good or bad the republic begins, it should be noted that in order to actually win the campaign as a Republic (at least at Legendary difficulty) you have to stop at nothing lest you are crushed by the combined forces of everyone. One of the few examples of a victorious Republic campaign at Legendary difficulty is one in which the Josai Republic raped Japan in order to sustain itself. With trade income down to zero (no allies and foreign trade constantly raided), the Republic never managed to get positive income, and was forced to constantly plunder every city they captured to avoid bankruptcy, then proceed to raze every building in the city they had no hope of holding just to weaken the enemy. By the end of the campaign, the victorious Republic had left Japan in shambles, with most provinces completely impoverished and rebels roaming the land. Talk about Pyrrhic Victory...
In Medieval II, when you defeat enemies while they rout you take prisoners. After a battle, your normally get a choice: Execute them outright, release them outright, or hold them for ransom, either seeing them released in exchange for money or you get nothing from their faction and have to execute them. At the bottom right hand corner of the battle map's controls, you see a number of prisoners you take during the battle. This counter rises as long as you are taking prisoners. However, when fighting Rebels, no matter how high the counter goes you never get the option to ransom them. And when discussing rebels, your generals will mention that they "so richy deserve the gallows"... do the math.
If you're worried about losing Chivalry points or gaining Dread, no one seems to care about what you do to rebels. In fact, for all intents and purposes you may as well have just killed them in the battle itself like in Rome.
In Medieval II, if you choose to execute prisoners or the enemy doesn't pay ransom, you hear the rather gruesome sounds of them being executed. Some of them are obvious, like choking sounds indicating a hanging, or gunfire indicating firing squads. But one sound just consists of a horse's hooves, a man screaming, and messy blood splatter. In other words, it's the sound of prisoners being drawn and quartered.
