OF all the doom-laden headlines this week as we edge ever closer to the abyss that is war - an abyss so deep we can't see the bottom and have no idea what'll happen to us if we are pitched into it - the one that must have filled anybody who ever went to school with the most dread came from the Balkans.

"Leader assassinated; Serbian nationalists suspected."

The essay that every schoolchild knew would be on the history exam was: "Discuss the causes of the First World War." And so Wednesday's news about the assassination - possibly by nationalists - of Zoran Djindjic, the Serbian leader, was a truly worrying moment for all who had been paying attention in class.

On June 28, 1914 - a date as famous to one century as September 11, 2001 will become to another - Archduke Franz Ferdinand, heir to the throne of Austria-Hungary, was assassinated in Sarajevo by a terrorist called Gavrilo Princip.

Austria had occupied Bosnia in 1908 to keep Serbia out and, by 1914, tension was high among the Bosnian Serbs, of whom 20-year-old Princip was one.

Franz Ferdinand's father, the emperor, forced the Archduke to go on an official visit to Sarajevo. The archduke had bad premonitions, especially when his train broke down before he had even arrived.

"You see, that's the way it starts," he said to his wife Sophie. "At first the carriage running hot, then a murder attempt in Sarajevo, and finally, if all that doesn't get anywhere, an explosion on board the ship!" He was right - but he didn't reach his ship.

He was driven into Sarajevo in an open topped carriage. Six conspirators armed with revolvers and bombs were waiting for him. The first three bottled out; Princip was the fifth, but the fourth - Nedeljko Cabrilovic threw his bomb, which bounced off the Archduke's car.

Immediately the Archduke's convoy speeded up, and it whizzed past Princip. Disappointed, he consulted his newspaper to see the route of the Archduke's return journey, and decided to take up a position in Franz-Josef Strasse.

Of course, security planned another way out - but they forgot to tell the chauffeur, Leopold Lojka. And Lojka turned into Franz-Josef Strasse. The Archduke's men started shouting at him to turn back. Lojka slammed on the brakes; the car crawled to a halt directly in front of Princip.

He took aim with his revolver, but a policeman knocked his arm down. Another Serb nationalist jumped on the policeman; Princip turned his head and fired twice without looking. One bullet struck Sophie in the abdomen, the other hit Franz Ferdinand in the neck. Both died within minutes.

An angry Austria-Hungary declared war on Serbia; Serbia's ally Russia mobilised its forces. Austria-Hungary turned on Russia; Russia's ally France turned on Austria-Hungary. Austria-Hungary's ally Germany turned on France, invading her through neutral Belgium. And Belgium's ally was Britain who, on August 4, declared war on Germany.

The rest is history. An assassination in the Balkans embroiled 32 countries in a war which killed 11 million.

Of course it won't happen this time, but when you start lobbing bombs around in fraught regions, you have no idea what accidents of history you might unleash.