WW1,which started because of the stupidity of the European monarchies and their massive egos.WW1 saw the end of many of the European dynasties
On the contrary WWI was the result of chauvinistic *popular* nationalism combined with the dominance of military general staffs over the diplomats and political decision-makers.
The royal families of Europe were all heavily intermarried, and not at all keen to go to war with cousins and siblings and uncles, but the reality is that they no longer really called the shots within their states thanks to modernity. Unlike the medieval era royal marriages were no longer enough to keep the peace. Writers, generals, bureaucrats, industrialists, the middle class all had far more say.
Slavs demanding an end to German and Hapsburg control within the Austro-Hungarian Empire, Russians aiming to help ethnic compatriots, Germans keen to help fellow Germans and cement continental power, the French determined to avenge the humiliation and territorial losses of 1870, etc.
War in August 1914 seemed like it would be a short and exciting game to the masses, elites and generals alike. No one really understood how technology had transformed everything, or the kind of endless grinding mass slaughter that these changes would produce.
The manner in which no one stood up to his annexation of Austria made him confident of the weakness of will of the rest of the European nations and he unleashed the dogs of war into Czechoslovakia and then Poland.
Not even the German public expected Hitler to attempt to go beyond the unification of ethnic German areas in Central-Eastern Europe, and the restoration of Germany's status as a great power.
Even though Hitler had sketched out his vision of eastern Lebensraum in his Mein Kampf and in some speeches, no one thought he was quite mad enough to go through with it.
It was only when Hitler ordered the occupation of non-German Bohemia and Moravia in March of 1939 that it became clear that he really intended to go beyond 'self determination of Germans everywhere'.
Most of the other players (even Stalin) assumed Hitler was rational in his risk taking, and were willing to make concessions up to what they imagined were the limits of his ambition, which Hitler irrationally interpreted as weakness.
Most dictators value survival above all else - yet Hitler preferred a glorious annihilation to any sort of climbdown that would let him live to fight another day. In that sense he was a freak of nature that no one anticipated . All of the players learned too late that there was no limit to his ambition, or the kind of risks he would take.
