People, kingdoms and nations went to war for many reasons, from oppression, to "marriages" among royals, land grabs, consolidation of power in order to have more political stability (fewer incursions from usurpers of the kingdom), affronts, insanity, etc. but I can't imagine many were due to "we have too many restless men" we need to concoct war, risk losing war and our people, because we have too many young men and we need culling because....
A standing army plus reserves and the population you could call up to fight is what kept enemies from wanting to invade.
I remember reading about this very thing in Barbara Tuchman's "A distant Mirror". In medieval France there was a large number of bandits that looted the countryside and wreaked havoc wherever they went. The royalty would find some excuse to wage war and hire a general to round up the bandits and bring them away with promises of war bounty. In the scope of world history, though, this was probably not too common.
If you actually study the history, the single most common reason that people go to war is due to a lack of resources of some sort. Food or something critical to the economy or whatever. (Edit: There are a MILLION explanations, but scarcity of resources or insufficient resources of some sort is almost always the actual root cause.)
So, again: "There aren't enough resources" is essentially what people mean when they say "There are too many people." Sending people to war -- win, lose or draw -- tends to get the number of people down and may have long term impact on keeping the number down by removing the potential for those who died young on the field of battle to reproduce at all.
You can claim all you like that "BUT, THAT isn't THE REASON we go to war" and, you know, it just makes me think you have no understanding of history. It doesn't convince me you are right.
Broadly speaking, you are right. "I want your land" can be interpreted as meaning "I don't have enough land" and need Lebensraum.
The Spanish conquest of the Aztec Empire could be interpreted as Spain not having enough gold, land, and people.
The US invasions of Panama and Grenada could be interpreted as due to a lack of pro-Americans in power in nearby countries.
The Norse fights with the Dorset and Thule "skraelings" could be interpreted as due to a lack of desired cultural homogeneity.
But it's hard to make sense of anything at that level of generality. To push it a notch higher, I could say that wars are due to specific arrangements of atoms. I would be absolutely correct, but it wouldn't be helpful.
If by men you mean people, ok. But he said too many "men". But its still backwards, its like when someone says, oh my food is too cold and you say, no, it's not too cold at all, it's simply not hot enough.
Often times wars were fought for stability. If you were stronger the weaker adversaries would be less likely to wage war against you. So your going to war was more to counteract someone else's lack of resources who might fight for them rather than your need for resources...
Anyhow it like saying we went to war because we wanted to live longer.... Ok. Yes, but that's not how we typically present the issue.
So your going to war was more to counteract someone else's lack of resources who might fight for them rather than your need for resources...
This is causing me a blue screen of death moment. You are disagreeing with me by saying "But the war could start because of someone else's lack of resources..." and I cannot fathom how that is an argument against the idea that a lack of resources is almost always the root cause.
So, I think I shall step away from this discussion now.
A standing army plus reserves and the population you could call up to fight is what kept enemies from wanting to invade.