Hundreds of millions of people will die and billions will suffer the consequences of war, depression, fascism, communism, and ethnic cleansing. You also have to cynically note that Serbia and Bosnia in 1914 were blood brothers willing to fight a hopeless war against the Great Powers together, but by 1999 they can’t co-exist in the same space without both sides trying to exterminate the other. They fight a war at the beginning of the 20th century in the name of unification, and fight a war at the end of the 20th century in the name of separation. If there is a God, Yugoslavia is his sickest and cruelest joke.
If you don’t know what I’m talking about, I’m talking about a Bosnian terrorist shooting Archduke Ferdinand I of the Austro-Hungarian Empire because he wants Bosnia to be independent so it can join with Serbia. Austria demands an apology and a confession that Serbia instigated it. They get it, then say that isn’t good enough and mobilize for war. Czar Nicholas II of Russia, never one for good decisions, sees an opportunity to help his Slavic brothers out and take control of the Balkans, so he mobilizes his army for war.
Kaiser Wilhelm II of Germany also sees a good chance to increase the prestige and influence of central Europe and remove the long-standing thorn that is the Russian czar. Wilhelm is also eager to disprove critics who say he can’t fill Bismarck’s shoes, so he enthusiastically orders the German Army to mobilize. Unfortunately, he doesn’t understand that Bismarck left behind a military culture in which “mobilize” meant “war”, that part of Germany’s preparations for war include securing its weak flank because mobilization to the generals means Germany’s leadership thinks that war with Western Europe is inevitable. He wants the army to mass and does not declare war, but Germany’s political leaders realize they’re at war when they get reports that the German Army has captured the Belgian border fortress at Liege, and France and Britain have declared war on them.
World War I is that stupid.
Mobilization of resources were surprisingly slow in World War I, especially considering that all of the Great Powers had anticipated just such a war for decades and all had war plans for specifically this contingency. The beginning phase of the war looked very good for the Central Powers, until they outran their supply lines and settled into trenches to avoid flying death from machine guns. Every government tried to run some variation of a command economy, each believing that a centralized authority could directly control economic resources for war. You see varying results, from Russia spending itself into nonexistence to Germany mobilizing so well that it inspired Lenin that government should control the entire economy all the time.
The aftermath completely changed the face of war, economics, and history. This would be the last war in which more soldiers were killed than civilians. It was the first time that the major costs of war were born by the winners, not the losers. The Treaty of Versailles demanded “reparations” from Germany, money that the Allies would never see and would eventually have to pay themselves. France waited patiently for 2.5 years’ worth of GDP to be paid by Germany and Russia for war debts, money that would be repudiated by the Nazis and the Bolsheviks; 15 million citizens died of starvation and influenza while they waited for the check. The end of World War I also meant the end of European monarchies, as dynasties collapsed and abdicated their powers to parliamentary democracies (power given to returning generations of fighting men), some of which gave way to absolutist groups like the communists and fascists.
Citizens would no longer blithely believe that progress, evolution, and utopia were functions of Adam Smith’s invisible hand. It is impossible to look through the history of World War I and come out as a liberal believer in peace as a default condition for humanity, the benevolence of the market, the eventual triumph of reasoned discussion, or that equilibrium for humanity is an inevitable upward rise. Capitalism had to go back to the drawing board, muddling through and trying to cobble together some kind of new cohesive theory that looks kind of like pre-World War I philosophy but make it true in practice, even if it doesn’t always make sense.