One hundred years ago today, the assassination of the archduke of Austria at Sarajevo triggered the bloody, destructive conflagration of the world’s nations known as the Great War.
Ralf Raico offers an excellent panoramic account of the origins of World War I.
As for economic causes and consequences, make sure to read this article in which David Stockman explains that
[...] the Great Depression was born in the extraordinary but unsustainable boom of 1914-1929 that was, in turn, an artificial and bloated project of the warfare and central banking branches of the state, not the free market. Nominal GDP, which had been deformed and bloated to $103 billion by 1929, contracted massively, dropping to only $56 billion by 1933.
Crucially, the overwhelming portion of this unprecedented contraction was in exports, inventories, fixed plant and durable goods—the very sectors that had been artificially hyped. These components declined by $33 billion during the four year contraction and accounted for fully 70 percent of the entire drop in nominal GDP.
So there was no mysterious loss of that Keynesian economic ether called “aggregate demand”, but only the inevitable shrinkage of a state induced boom. It was not the depression bottom of 1933 that was too low, but the wartime debt and speculation bloated peak in 1929 that had been unsustainably too high.