> Another is the destruction of the library at Alexandria, which was supposedly done by accident, against orders. Had that not been destroyed would we be substantially further ahead now?

I doubt it made much difference to progress. Having knowledge locked up without the culture that made it is not that helpful.

On the other hand, the destruction of Baghdad by the Mongols had far reaching impact. Not only were the books destroyed (supposedly the river ran black with the ink of all the books tossed into it) but the populate was massacred (after which the river ran red with blood).

This had a profound effect on the Arab/Muslim world that I think is still felt to this day.

It still amazes me that over 2,000 years later we have the direct writings of Julius Caesar of his various campaigns. I believe these texts are still used heavily in teaching Latin because the language is so clear. Obviously there's bias involved in his accounts but they still represent an extraordinary first hadn account of Roman conquests.

Dan Carlin has an episode on what he calls the Celtic Holocaust, the conquest of Gaul (ie modern day France). It's called this because it's estimated a third of the population was killed in the process. From a historical perspective, Caesar also could've lost here, which again would've massively changed history. There would be conquering and settling of Britannia without Gaul. And Britannia was important for many Roman emperors after that (eg Constantine, who converted Rome to Christianity, was proclaimed emperor by his troops in modern day York).

Anyway, part of what drove the Roman psyche with Gaul was that early in Roman history (the 4th century BCE IIRC), Rome was sacked by the Gauls. It's why we don't have much history before this and why the origins of Rome are shrouded in mystery and legend (ie most view the tales of Romulus and Remus as apocryphal at best).

But historians make the case of why conquering Gaul was so important to Rome. I was reminded of this when you mentioned the conquest of Baghdad. The damage can be well beyond the loss of culture or literary works.

My understanding is that Julius Caesar could have lost that war but there is little chance that Rome wouldn't have submitted Gaul in the end.

Current Spain and Portugal's territory required from Rome no less than 190 years of wars. Romans kept going on submitting a few tribes there every year for two centuries.

A sort of "proof" of this assertion is that Rome, in the end, conquered all territories around the Mediterranean Sea and far beyond. Of course, the course of events are by nature unpredictable but I find it reasonable tosay that the odds for a long term victory of Gaul were slim.

However, but that was much earlier, the two Punic wars against Carthage were much more existential threats to Rome.