As long as war remains wildly profitable, war will continue - and war always has been profitable, and likely always will be - right up until the point that there’s nothing left, and the profiteers realise they can’t eat a number in a ledger.
No, this is a relatively new phenomenon that arose after WWI, when warfare became highly industrialized and too costly to fight personally for the rich.
During WWI, the aristocracy led from the front, as was their traditional calling, and they were mowed down in droves just like the most common soldier.
For the British, an entire generation of their sons were killed at Marne, Verdun, the Somme, Ypres, and other large battles, and the effect was stark:
At the outset of the 1870's, the British aristocracy could rightly consider themselves the most fortunate people on earth: they held the lion's share of land, wealth, and power in the world's greatest empire. By the end of the 1930's they had lost not only a generation of sons in the First World War, but also much of their prosperity, prestige and political significance. [1]
This largely held true for the Austro-Hungarian elite (they were decimated and the empire was torn apart), the Germans, and every other participant in the fight.
Note that historically, European aristocrats were military elites and were descended from the knightly class. The whole reason they were a cut above the population was because they would fight and take the danger first. The realization after WWI that war was simply a number's game doomed the legitimacy of their leadership in all countries.
[1] https://www.goodreads.com/book/show/750411.The_Decline_and_F...
Yes, the early 20th century was a turning point, but it only changed who was profiting.
Even at the turn of the century, the foundation of the wealth of the British aristocracy rested on ownership of land, agriculture, and control of the Empire. The Great War disrupted all three greatly.
It was mainly the merchant and upper middle class that owned stocks, ran businesses, and profited from the war, with a tiny fraction of aristocrats benefiting.
Most of the rest saw the value of their land go towards zero, their manors used for wartime purposes while their servants were conscripted away, their sons killed on the field of battle, and confiscatory tax rates imposed to help fund the war effort.
This pattern was repeated again in WW2.
There's a reason Downton Abbey is set on the eve of WW1 and goes into the interwar period — that's when the British aristocracy was systematically taken apart piece by piece.
Common people largely supported monarchical, aristocratic governments before WW1. One reason was because their elites that actually put their money (and their lives) on the line for their nation... although sometimes with disastrous consequences.
Note that historically, the world wars were when wealth inequality dropped the most quickly. The US raised marginal tax rates to 90% during WW2, and most wealth was real assets, which obviously suffered greatly all throughout Europe. In a total war, everyone can give up their lives, but the wealthy can also lose their wealth.
You wrote that wars being a profitable enterprise is a relatively new phenomenon that arose after WW1. What I'm saying is that pre-WW1 wars were already a profitable enterprise (for that aristocracy - exactly in terms of extra land, etc), and that WW1 only changed who profited from them.
And for example, U.S. casualties in Iraq and Afghanistan for the last 15 years is ~4,424. Being in the army in the U.S., UK, or nearly any advanced nation today isn't quite the meat grinder that WWI was.
I mean one of the big ones is that WWI was atrocious for infantry because the tactics were 19th century, but the weapons were 20th century. IE generals were fighting the war like there weren't machines guns, chemical weapons and a laundry list of revolutionary developments that made outdated tactics just devastating.
A lot of wars have been fought since then and our tactics have adjusted quite a bit. Which means we're generally not sending wave after wave of men into entrenched enemy fortifications and railing about their cowardice when those assaults fail or saluting their "heroism" when those units are wiped out to the man.
We've got better protection and better medical care leading to higher survivability. We're not in a state of total war, and we're not anywhere near close to talking about lost generations from current conflicts.
Probably most of the posh people you know came back whole. Well that didn't always happen and amount of risk certainly tempers many peoples decisions about whether to serve in the military if they have options.
And frankly given a choice between serving in the darkest days of WW1 and a current conflict wouldn't be a tough choice for many soldiers.
Incidentally, in the Civil War and all previous Anglo-American wars, you could literally buy your way out of a draft.
War is popular. I mean, look at how much of our modern entertainment glorifies war. The military is generally and genuinely the most popular public institution. The problem is, when a war loses its momentum, people lose their enthusiasm really quickly. People forget that the Iraq War, for example, actually had majority support when it broke out.
War profiteers certainly exist, but they are a tiny minority, even of the military-industrial complex. There is a much larger segment of industry that is hurt by war: war means a loss of external markets, disruption of supply chains, increased cost of resources, higher taxes, lower internal demand, and massive destruction of property (should the war be fought on your soil).
War is not profitable. The one thing that war is most closely connected with is higher taxes. The inability to pay for wars is probably the single largest contributor to the downfall of governments in recorded history.
Saddam Hussein had been playing a game of pretending that he had WMDs throughout most of the 1990s up to the Iraq War. The US intelligence community took those claims too much at face value, and when the UN inspectors went in to evaluate the evidence, they didn't say that Iraq had no WMDs, they said they couldn't find evidence of WMDs but the Iraqis were being too shifty to draw a firm conclusion. Unfortunately for Saddam, the Bush administration took this only reinforcing earlier beliefs that Iraq was fundamentally untrustworthy and hell-bent on WMDs, and was willing to go to war even without rock-solid evidence (unlike the EU, which saw the lack of evidence as a good reason to do nothing).