Or at least it used to be asked no one bothers to ask it these days because (a) our educational standards are too terrible to ask questions like that and (b) the answer is pretty obvious. Just look around you for about three seconds and you've got a pretty good clue.
In the case of Rome what went wrong was that they won a war. The Second Punic War to be exact.
Punic II: The Hanniballing, was a disaster for Rome. They lost their best and their brightest by the tens thousand, with the pinnacle of the slaughter being at Cannae, where it was discovered that it takes about six hours to kill one hundred thousand men by hand.
Rome won the war but the cost was their faith in themselves.
A downward spiral began that degraded the pillars of their Republic.
Rich Romans became very rich and the poor Romans became desperate. Farmers were forced off their land and moved to the City itself just to survive on the second century BC's equivalent of the EBT card, the Grain Dole.
A series of strongman First Citizens began, each leading his own faction in political dominance. First the Gracchus Brothers, next came Marius, then Sulla, followed eventually by Pompeii. The last First Citizen of the Republic was Gaius Julius Caesar.
The first Emperor of Rome was Augustus. The Roman Senate still existed but it was very much a junior partner after that. The Roman Republic existed only as a few trappings from then on.
The point that I am skirting is this. There is a thing called a fatal but not immediately disabling wound. A man who has one of those can still do a lot fighting and killing even while his life blood pours out. The same is true of a civilization. Even after the wound has been dealt it can continue to fight...It can in fact conquer the world. But that won't undo the fatal injury. It took Rome's one hundred fifty years. Ours has taken about that long.
The death of our civilization began in 1866.
It was the first period of the One Hundred Year German Unification War. I am the only on who calls it that. It gets taught in history books as four separate wars but enough time has passed that it's time to look at the forest instead of just the trees.
The Brothers War between Prussia and the Austro-Hungarian Empire was that rarest of things, a victorious war.
"Victory is a mirage in the desert. Where you end up is never where you thought you'd be when you started."
Yet the Brothers War between Prussia and Austria in 1866 actually was successful...From Bismarck's stand point anyway.
Bismarck was a man of simple desires. He wanted a united Germany under his boss Wilhelm III of Prussia. And he wanted that Germany to be the most powerful state in Europe.
A face only a walrus could love.
Up until that point the German states weren't united but with the rise of Nationalism it was starting to sound like a good idea to everyone, except the old Hegmon of the German peoples, Austria.
The Brother's War achieved all of Bismarck's goals and better still didn't set things up for a disastrous and unplanned second war. The power of Vienna over the German states was broken and replaced with a Berlin hegemony. The political power of the Hapsburgs was crippled.
Now mind you Bismarck had to fight to tooth and nail to get peace on his terms. And the thing was he had to fight his own army to get it.
The Wehrmacht wanted a heavy war debt placed on Austria-Hungry, provinces shaved off and a humiliating victory march through the street of Vienna. Wilhelm the Third (and First) was in favor. Crown Prince Frederick who hated Bizmark, never the less backed his play and the Chancellor defeated his king.
Round One, Proto-Germany.
Next on Bismarck's list was breaking the dominance of France. France had been the biggest fish in any European pond for some time. Everyone figured a war between Prussia and France would go France's way big time. However the French were seriously behind the times in terms of military technology, tactics and strategy. When Bismarck got France to declare war on Prussia, the Wehrmacht moved so fast it steamrollered the French army. Breaking it completely at the Battle of Sedan.
This is what defeat looks like.
It's a good idea to avoid it.
Mission accomplished at that point so far as Bismarck was concerned. Just get a peace treaty, a small war debt and head back home.
This time Bizmark lost. The Wehrmacht marched on Paris and shelled it. There was a humiliating victory parade through it's streets. A crushing war debt was placed on France. And just to make sure the bad feelz never went away, the provinces of Alsace and Lorraine were annexed.
Bizmark did manage to turn Wilhelm the Third of Prussia into Kaiser Wilhelm the First of a Germany.
But the price tag for this was a France that would stay at Germany's throat for the next seventy years.
This was the trap that snared our civilization. This was what set us up for the lethal but not immediately disabling injury. The coming mortal blow of the Great War.
The Death of Civilization Part II: The Shadow of Death