Good morning, everyone!
I began wondering about the population of New Vegas and the size of the NCR Army, both in the Mojave and in total.
I'm going to argue that the population of New Vegas is between ten and twenty thousand people. I base this off the size of Shady Sands shortly after the founding of the Republic, the rather high standard of living in New Vegas (as in, electricity, clean water, security by House and the comfort of the hotels), and the large number of tourists the Strip would attract.
Now, the population of the NCR is in the millions (a fact I've seen disputed in this forum before). I think that 2,000,000 is an acceptable estimation. From that, one can safely assume that the NCR Army numbers roughly at 100,000 (5% of the total population, a large proportion). I'm going to have to say that an NCR force of roughly 15,000 deployed to the Mojave is relatively accurate. Since Caesar's Legion is made up of 87 tribes, with a few hundred people in each tribe, I'm taking a guess and saying his forces are around 20,000.
Anyway. I open this thread up to discussion. My guesses are pretty lowsy (since it's 4:20am), so let's discuss!
Only 2 million? A lot of territories that were independant in the Fallout 2 era, roughly 40+ years ago, are now a part of the NCR. It's expanding north into Oregon, East into parts of Nevada, and South into Baja California, that's a LOT of prime real estate, and who knows how dense these areas are populated. For their army, I suppose 5% of the pop. seems accurate, considering they are still fighting the BoS, while expanding outward, not to mention keeping the Legion at bay. Also, their long history of being surrounded and besieged by enemies would undoubtedly compel them to maintain a sizable military. Plus, their military enlistment is open even to ghouls and even conquered peoples (Manny Vargas and Bitter-Root were once Khans, I believe.) which would give them a MUCH bigger pool to recruit from.
As for the population of the Mojave, I think 10-20 thousand seems about right, depending on how Outer Vegas is populated (I don't think most of the people that can afford the credit check to get into The Strip itself are locals). The rest of the Mojave is largely unsettled frontier land, with only a handful of major settlements in the desert.
As for the Legion, it's tough to say. They are a largely pre-industrial, agrarian state as far as we know, and without modern medicine available in sufficient quanatites amongst the general population, it's reasonable to assume that they have pre-industrial lifespans (in other words, short) and therefore a smaller population that requires the constant assimilation of tribes in order to keep its numbers up. But since in-game there are no indications that they are outnumbered by the NCR, I would say their force in the Mojave is somewhat higher than 20,000. Considering the NCR's massive advantage in firepower, the Legion would actually have to outnumber the NCR in-theatre by quite a bit to pose the threat they appear to in the game. I believe Lanius did say something about how it took them three years to aquire enough ammunition to launch their assault, so they might be investing a disproportionatley large amount of their military into this campaign.