After the fall of the western Roman empire, it was the Church that united Western Europe and provided a sense of European identity. That religious tradition would persist and spread, ultimately extinguishing the so-called “pagan” religions, despite the political fragmentation left in the wake of the fall of Rome. The one thing that nearly all Europeans eventually came to share was membership in the Latin Church (a note on nomenclature: for the sake of clarity, this chapter will use the term “Latin” instead of “Catholic” to describe the western Church based in Rome during this period, because both the western and eastern “Orthodox” churches claimed to be equally “catholic”: universal). As an institution, it alone was capable of preserving at least some of the legacy of ancient Rome.
That legacy was reflected in the learning preserved by the Church. For example, even though Latin faded away as a spoken language, all but vanishing by about the eighth century even in Italy, the Bible and written communication between educated elites was still in Latin. Latin went from being the vernacular of the Roman Empire to being, instead, the language of the educated elite all across Europe. An educated person (almost always a member of the Church in this period) from England could still correspond to an educated person in Spain or Italy, but that correspondence would take place in Latin. He or she would not be able to speak to their counterpart on the other side of the subcontinent, but they would share a written tongue.
Christianity displayed a remarkable power to convert even peoples who had previously proved militarily stronger than Christian opponents, from the Germanic invaders who had dismantled the western empire to the Slavic peoples that fought Byzantium to a standstill. Conversion often took place both because of the astonishing perseverance of Christian missionaries and the desire on the part of non-Christians to have better political relationships with Christians. That noted, there were also straightforward cases of forced conversions through military force - as described below, the Frankish king Charlemagne exemplified this tendency. Whether through heartfelt conversion or force, by the eleventh century almost everyone in Europe was a Christian, a Latin Christian in the west and an Orthodox Christian in the east.