Summed up nicely in four maps:
At this point, Christianity was a tiny fringe religion, and Christians were being persecuted off and on. Christians possessed effectively no political, economic or military power.
500 years later, Christianity had spread to the entire Roman Empire and beyond. In the East, the Eastern Roman Empire did in fact put Imperial Authority behind the Church – meaning, in practice, trying to adsorb all church authority under state authority. This lead to a lot a conflict, attempts to install heresies as the state religions, exile of uppity bishops who dared call out the flaws of the Empire and its leaders, and, in general, it was a messy relationship.The Church has pretty consistently been for what we now call the Separation of Church and State (“render unto Caesar”, and all that) out of the painfully learned lesson that Caesar is also a jealous god, and, being wise in the ways of the world, will dominate and use the Church for his own purposes.
What it didn’t result in was Christian Armies fighting battles of conquest and forced conversion – notice how the Empire, once Christian, shrank. Especially notice the West, where Gaul, Hispania, England, the Slavic countries and, indeed, much of Italy itself was no longer even nominally under the control of the Empire. The Visigoths had sacked Rome in 410, took central Gaul as their new homeland, but were driven southward into Spain by the invading Franks, who in turn were being driven west and south by other barbarians from the steppes. It was a chaotic and, yes, dark time.
In 632, a tribal warlord named Mohammed died, and left a small empire on the Arab Peninsula to his generals, and a conquering faith to his followers. Those generals lead those followers in wars of conquest, seizing and forcibly converting all of the Levant and all of North Africa in less than a 100 years, going so far as conquering Spain and half of France. In the East, the remnant of the Roman Empire, which had been hammered by barbarian incursions for centuries but still represented the only substantial organized military force encountered by Islam, saw the bulk of its territories (notably Egypt and the Levant) fall – but did manage to survive and hold the line against the invaders for another 8 centuries. In the West, a barbarian Frankish lord who happened to be a student of Roman military practices assembled an army of heavy infantry, and, in 732 at the battle of Tours in central France, turned back the invaders. Charles Martel’s victory marked the beginning of the Reconquista – the centuries long battle waged to recapture the Iberian Peninsula from Islam that succeeded in 1492 – 750 years after Charles the Hammer stopped the initial invasion.
But the slow success in the West was more than matched by the slow destruction of the East, until, finally, an Islamic army besieged and sacked Constantinople in 1453, and, as was the custom for cities that resisted, slaughtered everyone there. With the Byzantine Empire finally out of the way, the Turks resumed the march of Islam into Europe. Islam under the Turk slowly but consistently gained territory in Europe, going so far as to besiege Vienna twice (the city was heroically and epically saved both times), and attempt conquest by sea, which in 1571 was halted at the epic Battle of Lepanto.
The tide has never really turned – the Turkish Empire persisted until 1917; Western conquest of Islamic countries is an entirely modern and limp-wristed affair, not religious battles with forced conversions. The Western conquerors could hardly wait to get out, historically speaking. And so the conquered lands are returned to their ancient lords and to their ancient dreams.
Where we are today isn’t some new thing resulting from failed imperialism in the West, but an old thing, that only waits in brooding patience for the next chapter. It sees in these maps slow but inevitable victory.