I have a limited knowledge of this period, so excuse me if I make any incorrect assumptions, but it seems like the Roman Empire -- as large as it was -- was able to be successfully ruled by a single emperor for the first couple centuries of its existence. After the crisis of the 3rd century though, that seems to become an impossibility, with almost every new emperor (with a couple notable exceptions, i suppose) seeking instead to delegate parts of the empire to co-regents. I've always heard people say it was because the empire had become too large and unwieldly, but the empire was about the same size as it was (or smaller) two centuries before.

Is this just evidence of weak leaders seeking to mollify rivals for the crown? Is it a symptom of a deeper social issue, where Romans on one end of the empire feel more allegiance to their local leaders than they do to Romans on the other end of the empire? Is there some sort of breakdown of Roman nationhood? Is it more structural, are the means of communication between ends of the empire worse in the late 3rd or 4th century than they were in the 1st? Is society in general more divisive than it had been? Would a Roman living in London and a Roman living in Alexandria have more or less in common in the 1st century vs the 3rd/4th?

I realize I'm starting to stray into the broader question of "why did the roman empire collapse" but I'm really hoping to just stay focused on this one aspect, since I know that'd be opening a can of worms.

For example, if I was in Eqypt in lets say 1500 BC what would I have called it then?

Also, people around the time of Jesus and just after. Did they consider that the start of BC? Or did the "BC" time that we use today come much after?

I often hear it stated that many pre-Columbian cultures (especially the Maya) had a well developed knowledge of mathematics, but I've had a hard time finding good information about precisely what kinds of mathematics they were able to do.

It does seem like a lot of their math was related to their study of astronomy, like the Greeks. Is there any evidence that they had any knowledge of, for example, trigonometry or conics? (both of which started in the West as tools for Greek astronomy)

I would be especially grateful if anyone would be able to recommend some good books on this topic!

I was just wondering after watching Der Untergang movie.

Basically, what could one do with a lot of money in the old American west? Buy a better gun? A faster horse? In the movies, it doesn't seem like money could really get you anything but things that a normal person could already afford.

I've always been exasperated by arguments about whether the American Civil War was sparked by states' rights, or slavery. Would it be within the bounds of accepted scholarship to say that states' rights was the underlying cause of the Civil War, and that slavery was the proximate cause of the Civil War? I've heard from time to time that "state's rights" was just code for slavery, but I think it makes more sense to say that slavery was an example of state's rights, albeit the only one that mattered at the time. Thank you in advance for helping me understand where I'm right, and where I'm wrong.

Everything I've seen or read about the Mongols talks about how dominating the Mongols were in warfare, repeatedly defeating armies much larger than their own. But did they ever suffer any defeats themselves?

So I've just started reading into the 30 Years War, and I need something clarified. Were the Lutherans and Calvinists considered Protestants and roped into the same category at the time? My first book on the matter seems to think so, but when I tried to 'introduce' myself to the topic (via YouTube), I came away with a different impression.

Also, was there any solidarity between them, against the Catholics?

I understanding this must seem like a stupid question, but I'm really just now dipping my toe into a matter I know nothing about (which is exciting).

I know that I've seen very unfavorable opinions of his non-classical works such as "Carnage and Culture", which are very Huntington/"Clash of Civilization"-esque, but he first made a name for himself dealing with classical warfare, as I understand it, so is he better respected when he isn't straying outside his field?

Were they called home? Did any try to defect? Are any thought to still be "out there" working for Russia?

I was re-reading about the Boston Bombers and that question became relevant. Was it just because of Soviet influence in the middle east during the height of communism?

I was doing a project on Mussolini and I noticed something very interesting. Aside from him killing his political enemies, being Hitler's pal, and invading Greece and Ethiopia, Mussolini didn't seem all that bad in comparison to other WW2 Axis powers. Is this view of him correct, and if not, what else did he do? And if Mussolini was a dictator in modern times, how might he compare to Castro, Kim Jong Il/Un, and others?

If I remember correctly the nothing major happened during the middle of the Continuation War, the finnish army didn't want to advance. What was the finnish army doing during this time? What was the finnish high command thinking about? We're they thinking that Germany would succed? When did they start thinking about a German defeat? And how did they prepare for a Soviet counter attack?

I've seen that the Chinese were able to create repeating crossbows and wondered, were they ever brought over to Europe?

I know only a little bit about the English Civil War and Oliver Cromwell. Has there been any attempt at republican government or significant republican sentiment since those events?

I've been reading up on the Polish military and how they were, at least up until Stalin's death, forced to use Russian designed weapons. This got me wondering, how did the Eastern Bloc actually function internally?

Were the countries that weren't the USSR simply puppets, that had absolutely no say in anything whatsoever?

Or was it mainly the crew who died, making sailing further impossible?

Edit: And what was main part to aim for?

1. Was there any broad use of copper arrow-heads pre-Columbian?

2. Was there any broad use of iron arrow-heads post-Columbian?

How long did it take to transition to blackpowder weapons for non military use on the East Coast. If we need a specific place, then let's go with the Leatherstocking tales: up-state New York.

Me and few friends are discussing what Khan was like, we saw a statue of Khan and one couldn't believe that the Mongolians revered him to warrant a statue saying that it'd be akin to a Hitler statue (an exageration). So what was the Big man like?