In anthropology, this would fall under Robert Carneiro's theory on circumscription. Carneiro argued that population pressure due to running out of space or resources to expand was the primary cause of conflict, and from there the primary driver of state formation. It's not universally accepted, but it is still considered an important argument to take into account, at least within anthropology/archaeology.

Here is the original article: http://www.ncbi.nlm.nih.gov/m/pubmed/17820299/

And if you do a citation search from that point, you will find a lot of debate and Carneiro's own revisions and arguments.

However. That article came out in 1970 and Starship Troopers was written in 1959. So thats not where Heinlein got the idea from. But it is a defensible claim, theoretically speaking.

So all we need to do is find a war that is not based on population pressure. I wonder how the various internal Italian wars leading to unification can be seen as due to population pressure. Or the Italian invasion of Ethiopia. Or the English Civil War.

I suspect we end up re-defining "population pressure" to mean almost any economic or social cause. Or that we just take some minor aspect and turn it into the singular cause. So with the American Revolution there was an issue of expansion west. It was not the primary cause nor minor, just sort of middling.

The American Revolution seems like a pretty obvious counterexample.

The size of the American frontier provides perhaps the biggest release valve for population pressure since prehistory.

One of the slippery things about claims like these is the malleability of terms like "aggressor nation." I would claim that the colonists were the aggressors since the war came at a time of their choosing and for reasons of their choosing. Not only did the colonists have the frontier available to them, going to war with England would not solve population pressures because England was not confining the colonists to currently occupied land and the goal of the revolution was not to conquer England, thus providing for increased space for Americans to move into English territory.

If we turn the equation around, as defenders of claims like this always do, we see that the claim does not work for England either. Whether you are interested in defending the proposition (which I reject) that King George was spoiling for a fight prior to the revolution, it is clear that war with the colonies will have the effect of frustrating the release of population pressure rather than relieving it.

The colonies are already an excellent place to send excess population. War with the colonies will only disrupt the ability to ship people off there in the short term, and could (although in the real world it did not) have the effect of sealing the borders in the long term. There is nothing to gain in terms of population pressure to go to war with the colonies. Helping the colonists go to war with the Native Americans is consistent with the theory, but war with the colonists themselves is not.

Now, could you argue that colonies themselves are planted as a result of population pressures and colonies always eventually revolt once they become mature, so therefore a war with colonies stems from that original population pressure? You could make that argument, but doing so waters down the original claim so thoroughly that it saps much of its explanatory power.

Heinlein was fun for me to read when I was a reactionary teenager. I don't think taking him seriously as a thinker as an adult is the best idea.

The first issue is defining population and defining pressures. As was mentioned earlier a pressure on a resource is a pressure on population. So we must also define the word resource.

I feel that you cannot write off a conflict that is primarily forged through the ideals and wants of the ruling class as not being a population issue. Nor can I say power is not a resource. Power is definitely a resource, though not a tangible one, a very real one nonetheless.

The Spanish Civil War and the Norman conquest were power struggles between the ruling populations for power of the land. In the case of the 100 years war, it was actually also a war for physical tangible resources in land and what the land offered.

So the 100 years war is very clearly a population pressure war, and the Norman conquest due to a power vacuum. The Spanish Civil War was largely for the small folk fighting it a war over ideology but for the power classes and France, Soviet Union, etc. a war over the commodity of power within the region. (France and the Soviets weren't involved other then in giving military aid.)

There's the so-called Youth-Bulge theory which argues that, if a population grows faster than its economy, many young men can't find adequate jobs, thus lack in social prestige and have a hard time marrying, and thus turn to radical ideas and religious extremism.

Many wars can be arguably viewed as a fight for resources.

Hitler talked about lebensraum or living space by taking farm land away from other groups of people. The ultimate goal of this plan was self sufficiency, they did not want to be vulnerable to blockades (like they suffered in WWI).

In the French revolution the famous Women's march was caused not by ideals but by bread shortages.

Wars are just not often fought for food, but for trade routes. The suez canal crises was a fight over one of the most important trade zones in the world. Modern military actions in Somalia are fought to ensure access to safe trade.

The first Iraq war was fought to ensure access to oil...

The most wartorn countries in Africa are actually the ones with ressources. In ressourcestarved countries they actually had to work together to make something worthwhile without something obvious to fight over.

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, questions of this type can be directed to more appropriate subreddits, such as /r/history or /r/askhistory.

Perhaps /r/asksocialscience could also deal with this question, or /r/askanthropology.

Ok, sorry, let me clarify. Pinker brings a huge body of evidence, and significant statistical analysis, to bear on this and other theories as to reasons behind violence of this kind. I'll bow out of the discussion and be happy to retract my recommendation if what is required is a two-paragraph synopsis of a 500+ p argument with a ton of moving parts. I don't have the time to summarize it, so perhaps I should never have inserted myself into the discussion. I will simply suggest that if OP or anyone else wishes to pursue this line of reasoning, Pinker's book is an excellent one to add to the reading list.

No. Stephen Pinker tackles this theory pretty thoroughly and imho convincingly in his The Better Angels of our Nature: Why Violence has Declined.