The spread of Christianity, from antiquity until today, on an animated map

This is called being a “universalizing” religion.

The big three universalizing religions are Christianity, Islam, and Buddhism.

You can understand a lot of religious history as just those three religions expanding and displacing other belief systems.

Contrast with non-universalizing religions like Judaism, Hinduism, and Shinto.

That is one important aspect, but there are several to my mind

- Life in the bronze age was very rough, and quality of life in cities was basically inhumane. Women were highly represented among earliest converts, as Christianity comparatively was rather progressive and demanded baseline respect for them. Also, pagan religions of the time, despite cultural significance, didn't promise much of a payoff for plebeians for all their toil. Conversion was easy after Paul pushed the case that they shouldn't have to convert to Judaism, with all that would entail.

- Especially in the early days, this was very much a pacifist religion, in addition to having an apocalyptic fixation. To Rome, "Render therefore unto Cesar the things which are Cesar's" is a handy sentiment for the populace to have. They fought and won several uprisings just from the Jews who wanted their independence (and expected their forthcoming Savior would literally help deliver this), and the vast empire was beginning it's slow decline. Killing Christians and making martyrs out of them didn't make much sense in the long-run.

- There is a magic sauce in universalizing, it extends the shared culture within territories and makes it easier to convince people to wage war for you. Prior, the motivators were mainly tribal/blood connections, and money.

The Jews for their part were content with what they had, Christianity didn't provide much value-added, especially for the "zealots" who were ready to die for freedom. The "Love-thy-neighbor" sentiment is sort of similar to parts of Leviticus, but the cranked up pacifism and relaxed outlook over some rules was a departure. I think the "afterlife" bit was a lot more persuasive for gentiles. Then of course the rituals and conception in the collective consciousness evolved over time, from influences like Augustine and others.

By the time there was a true Christendom, powers that be dropped the (absolute) significance of pacifism, as that was no longer as useful as it was.

The reason Christianity spread so wildly is that Emperor Constantine found it more politically useful for Christians to die in his military than the lions den, so he put the military might of the Roman empire behind it. If not for Rome and the imperial powers that followed, Christianity would probably have died out like all of the other weird Jewish apocalypse cults of the day. We might all rather be Mithrainists or something.

How can “genocide” apply to a voluntary religious group? And even if it could, the linked wikipedia article doesn’t seem to support your claim, either. Do you have anything else we could review?

Citation needed. Since year 1300 or for 1300 years? The former is closer to the truth than the latter, AFAIK.

Not a lot different from what the Christians did to non believers in the West, really.

But was it doctrinally different from Chalcedonian Christianity to justify its own colour on the map. Wikipedia suggests no, which chimes with my understanding: some local minor differences in practice, but nothing like the Christological disputes that caused the rift with the Church of the East, nor like the row over papal supremacy etc. that led to the Great Schism between Roman Catholicism and Eastern Orthodoxy.

But the graphic suggests that Celtic Christianity was in some sense theologically distinct from Chalcedonian Christianity, and that doesn't seem to have been the case. The main ways that the Christians of Ireland and Britain differed from those of continental western Europe seem to have been in the shape of the monastic tonsure and the calculation of the date of Easter; and in the latter, at least, British and Irish Christians were in conformity with Rome by the end of the eighth century. (There was also an emphasis on penance and absolution as a private rather than public rite, but this was ultimately adopted by the wider church.)

There doesn't seem to have been any doctrinal disputes, nor any suggestion that British and Irish Christianity was in any way separate from the Church of Rome.

You’re pattern matching something like the Saxon Wars under Charlemagne. In this case missing idols probably owe more to wood not surviving a millennium in Swedish soil + converts destroying their own former cult objects.

First of all, you're confusing different events: iconoclasm was the destruction of Christian icons, by Christians who thought that practice was idolatrous.

> the battles were so bloody that the Christian victors not only converted the conquered

Who do you think 'conquered' the Swedes, some continental Frenchman? Their own kings converted, and thereafter converted their countrymen. And the first such Christian king, Olof Skötkonung, inherited the throne -- he didn't conquer it.

When western politicians and media lectures the world on human rights, I can't help but wonder how funny it is that because westerners front loaded their genocidal violence, they now get to feel superior to others that didn't completely wipe out the conquered.