[saiya-jin]

> at least as long as we take "strong men" to mean "powerful armies"

I've never understood it as you do - strong men are just strong men, no need to read between the lines (of 1-liner). If you stick to the original meaning, this saying is as valid now as anytime in the past.

Strong men know what they want and need and are not afraid to go for it, and most often also obtain it. Being able to defend oneself is another meaning. In opposite to weak men, who are unsure of themselves, don't know what they want out of life, expecting things to be handled to them and life figured out.

I don't know in which part of society you do exist, but anytime in my past and present both of those groups are/were well represented, and successful life is definitely a domain of the strong folks.

[simiones]

I've usually seen this quote as a meme applied to military power, usually accompanied by imagery of roman legionnaires or such. As far as I understand, the original quote is coming from a post-apocalyptic novel, so I doubt the context is supposed to be everyday life.

Even so, regardless of other context, the general reality is that wealth and power beget wealth and power. Poor people (or societies) have a much much smaller chance of becoming wealthy than people who start wealthy have of maintaining their wealth.

I would agree that it those extraordinarily few people who manage to ascend the social latter are probably universally very strong people. But there are many times more people who could be considered weak that nevertheless preserve their wealth and status than there are strong people who improve their own. This applies both at an individual level as well as a group and societal level.