One point on the beginning of The Great War. The assassination of the Hapsburg Archduke Franz Ferdinand (by accident, no less -Gavrilo Princip had given up his original plan after the Archduke's driver took a wrong turn, missing the assassin's intended ambush but later chancing to cross his path in the store where he'd gone to sulk) had very little direct result. Austria-Hungary demanded the extradition of Princip and generally blamed the government of Serbia for the assassin's actions. When Serbia refused or was unable to produce Princip, Austria-Hungary threatened war to punish the Serbs. This is when Russia became involved. Much as they did in the 1999 Kosovo conflict, the Russian government felt compelled to come to the aid of their Slavic brothers, and threatened Austria-Hungary with war in the east if they attacked Serbia. This is where stupidity and pig-headedness come into play.
- Pig-headedness, Part 1 - Pan-Slavism as well as the desire to increase his power and influence in Europe induced the Czar to press his case, making a potentially negligible Balkan conflict into a wider east-European war.
- Stupidity - The Hapsburg monarchy of the Austro-Hungarian Empire, which was collapsing from the lethal combination of republicanism in Europe and nationalism among its many minorities, who together far outweighed the "majority" Austrians and Hungarians, appealed to the German Kaiser -what would he do if they should be attacked by Russia? They were unable to defend themselves in that case. The Kaiser, perhaps not realizing the gravity of the situation, or perhaps simply feeling that the mere threat of war with Germany would make the Russians back down (either possibility requires blithering idiocy on his part), assured the Austrians that Germany would back them.
- Pig-Headedness, Part 2 - The Czar, knowing now that Germany would honor its pledge to defend Austria-Hungary, and that this large-scale war would activate the network of mutual defense treaties among the big countries of Europe (tantamount to "going nuclear" in Cold War parlance) attacked anyway. The rest, as they say, is history.
There is a Pig-headedness, Part 3 which involves France insisting upon blaming Germany for the war after the fact, (they were really out to get revenge for their defeat in the 1871 Franco-Prussian War) and demanding the harsh provisions of the Treaty of Versailles which did more than any other single historical event to cause the Great Depression, the rise of Adolf Hitler and the Second World War, but that's another node...