28 July—On this day in 1914, a month after Gavrilo Princip assassinated Archduke Franz Ferdinand—heir presumptive to the Austro-Hungarian Empire throne—and his wife, Sophie, Duchess von Hohenberg, in Sarajevo, Austria-Hungary declared war on Serbia. Within a few days, Austria-Hungary ally Germany declared war on Serbian tangential allies Russia and France and invaded Belgium as a strategic move (the notorious Schlieffen Plan) to essentially screw France. It was Germany, after all.

Little Belgium was neutral and the 1839 Treaty of London obligated Britain to defend her. So within the week, Belgium, France, Great Britain, Russia, and Serbia declared war on Austria-Hungary and its ally Germany.

Thus commenced what at the time was known as the Great War and with the outbreak of the Second World War came to be known as the First World War and World War I, even though World War II hadn’t quite become a world war in 1939.

So what was Franz Ferdinand doing in Sarajevo in June 1914? Well, Sarajevo was the capital of Bosnia and Herzegovina, which had been annexed (mostly by military rather than diplomatic means, of course) by Austria-Hungary in 1908 to assert her dominance in the Balkans. Officially the archduke was there to open a new museum and inspect his troops during summer exercises. Unofficially, to be sure, the whole thing was a show of military force simply to intimidate the nationalists who wanted unification with Serbia.

Nineteen-year-old assassin Gavrilo Princip was a fervent Serbian nationalist of questionable stability who was part of a conspiracy called Young Bosnia to end Austro-Hungarian rule over Bosnia and Herzegovina. Princip wasn’t at all remorseful about assassinating Franz Ferdinand but did regret killing Sophie as collateral damage. And the assassination was in fact seen by some as a legitimate (if not particularly appropriate) response to perceived oppression.

In all events, Princip and his accomplices were arrested after the assassination and tried for high treason and murder. The three over 20 were executed by hanging. Incredible as it may seem, the adolescents like Princip were too young for that under Austro-Hungarian law, so they were sentenced to prison terms of 20 years or less. One managed to escape to Montenegro.

And Gavrilo Princip himself—the actual trigger man—was sentenced to only 20 years, contracted tuberculosis which caused him to lose an arm, and died from it at the age of 23 on 28 April 1918. Just six-and-a-half months before 11 November 1918—Armistice Day, which marked the end of the war he had caused . . .