Medieval: Total War™ covers the period 1087-1453, a period of almost continuous warfare and strife in Europe.
"This was the time of Crusaders and Saracens, the Hundred Years War, the Holy Roman Emperors, heresy and inquisitions, the Reconquista in Spain, Teutonic Knights and boyars, the rise of the Turkish Empire, the Black Death, and the final fall of Constantinople… It was a time of intense competition between the kings, princes, religions, new nations and radical new ideas that would make Europe the cockpit of the world."
Warfare was the only way of life for the ruling class. Indeed, the power of your sword – and your army – pretty much defined what you ruled. At one point the kings of France saw their kingdom shrink down to little more than the area around Paris as the English and Burgundians thrashed their armies repeatedly. The Byzantine Empire had to face a constant war of attrition with the Turks and put up with western Crusaders marching through (and sacking the place) every once in a while. There were some rules, of course, but the medieval period was largely about the strong taking what they could. National boundaries had yet to be fixed, so it wasn’t unusual to find monarchs claiming to be the rightful rulers of huge tracts of their neighbours’ lands. Politics and warfare were personal and characterized by shocking pragmatism and a dog-eat-dog attitude. Two examples will suffice. Royal children would be bartered away in marriage contracts during infancy, if this brought their parents extra lands. Winning any dynastic dispute was everything – after the English king Edward II was killed by a red hot poker shoved up his bottom, the man ultimately responsible, Roger Mortimer, ruled England for years without any opposition or censure for the method of assassination.

In the midst of all this political turmoil, there was religious turmoil too. The Christian church had split into Orthodox and Catholic “wings”, and each had excommunicated the other as heretics. Islamic states – in many ways more civilized and advanced than their Christian neighbours – were seen as a terrible threat. The Pope was a prince in his own right with his own earthly ambitions, but he could also use the power of excommunication to damn his earthly rivals: hellfire was guaranteed for anyone who crossed him. And then there were the Crusades. The reasons for the Crusades are many and open to dispute. Some crusaders were undoubtedly motivated by faith; others went for money, land and glory. Certainly, some Crusaders were not particularly choosy in whom they attacked: in 1204 crusaders sacked Constantinople, an Orthodox Christian city at the time, on their way to the Holy Land. Violence was simply ingrained in the ruling classes and their underlings.
From time to time the Catholic Church, of course, tried to stop the endless slaughter by ordering universal Days of Peace, banning warfare on certain days of the week, and even by declaring crossbows to be un-Christian weapons (possibly because they made it too easy for the unwashed masses to shoot down their armoured betters). None of these things worked. At other times churchmen were to be found encouraging the flock to kill non-believers and heretics.
And in the middle of all that and almost like a punishment from God – and it was seen this way at the time – the Black Death (to translate) carried off a third of Europe’s population. The fabric of society was changed as scarce peasants could demand wages for their work and not be killed for their impudence!
By 1453 the borders of modern Europe were starting to emerge: the last vestige of the Roman Empire, (To translate) Constantinople, fell to the Ottoman Turks. The Crusades had achieved nothing, and would be largely forgotten in the Middle East for the best part of 600 years. In the west, the Hundred Years War (to translate)between France and England was over, but would leave a legacy of rivalry (and an English two-fingered gesture of contempt) that lasts to this day. It would take another 40 years for Spain to be wholly Christian, but Europe was no longer “medieval”.