The Boer War was the first, the war on terror the latest, Vietnam the longest and World War II the biggest.
But 100 years ago, an innocent Australia prepared for what would prove to be its bloodiest war by far.
World War I cut a swathe through the youngest nation’s youngest and ablest men.
From the trenches of Gallipoli to the horrors of the Western Front, almost 62,000 Australians laid down their lives, compared with fewer than 40,000 in World War II.
More than 330,000 Diggers fought for king and country, and two out of every three were killed or wounded.
Now they are all gone, friend and foe; when British-born sailor Claude Choules died in Perth in 2011 he was the last survivor of the 70 million men who fought in World War I.
Of all the battles Australians waged, the doomed Gallipoli campaign is the one that has stirred patriotic hearts through succeeding generations, partly because it was the first.
But though 8700 Aussies never came home from that abortive venture in Turkey, the death toll in France and Belgium, on the Western Front, was four times heavier.
On the Somme in 1916, Australia lost as many casualties in eight weeks as would be lost at Gallipoli in eight months.
As the Battle of The Somme opened on July 1, 1916, Britain suffered its heaviest losses ever in war – 19,240 dead among an appalling casualty list of 57,420 in a single day.
In five months of grim warfare featuring the world’s first tank battles, the Allies succeeded only in pushing German forces back 65km to the heavily fortified Hindenburg Line.
The Western Front was deadlocked from a few months after the war’s start in 1914 until a few months before its end in 1918.
It stretched in a continuous line of trenches from the English Channel 700km to the Swiss frontier.
Armies millions of men strong measured advances in terms of a few kilometres gained over several months.
Casualties from each big attack, or “push”, ran into hundreds of thousands on both sides.
The first mass global war of the industrialised age cost more than nine million lives and, according to one estimate, around $260 billion – six times the sum of all the national debt accumulated in the world from the end of the 18th century to 1914.
Australia, federated only 13 years earlier, was unquestioning in its loyalty to empire, with Andrew Fisher, the Labor prime minister, vowing to back Britain to “the last man and the last shilling”.
If Gallipoli was an ultimately futile baptism of fire, then worse was to come in France.
In 1916, Australians went through hell at Fromelles, where their enemy included a young Adolf Hitler, and in poison gas attacks at Pozieres, where Gallipoli hero Albert Jacka again distinguished himself.
In 1917, Diggers attacked famously at Bullecourt, and across the Belgian border at Messines and in the muddy battles of Passchendaele.
In 1918, commanded by Lieutenant General John Monash, they helped to stop the German March offensive and then to lead the advance to final victory.
One of their finest hours came in the attack that liberated Villers-Bretonneux on the third anniversary of their April 25, 1915, landings at Gallipoli.
Most Diggers came home appalled by war, but believing strongly in the need to commemorate it.
“The younger generation didn’t know the horrors of war. They need to be reminded,” said Ted Matthews, the last survivor of the original Gallipoli landings, who died aged 101 in 1997.
“That’s what their forefathers died for – to preserve their freedom and way of life.”
If the futility of the so-called Great War is puzzling to modern generations, its cause is even more baffling.
The spark was the clumsy assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, on a bridge in Sarajevo.
After decades of imperialist and nationalist tensions, backed by myriad treaties and alliances, it was all that was needed to draw in the great powers of Europe.
The assassin’s bullet was the “shot heard around the world”, but who today who could name the man who fired it, Serbian Gavrilo Princip?
The guns of war finally fell silent on the 11th hour of the 11th day of the 11th month of 1918.
World War I was widely expected on all sides to be over by Christmas 1914.
It was supposed to be the war to end all wars, but it served to set the stage for another global conflagration.
Within two decades the great powers were arming themselves for World War II.