They were never going to be able to contain themselves. For all the promises of a dignified commemoration, the Tory right's standard bearers held back for less than 48 hours into the new year before launching a full-throated defence of the "war to end all wars". The killing fields of Gallipoli and the Somme had been drenched in blood for a "noble cause", declared Michael Gove. The slaughter unleashed in 1914 had been a "just war" for freedom.

Hostility to the war, the education secretary complained, had been fostered by leftwingers and comedians who denigrated patriotism and painted the conflict as a "misbegotten shambles". Gove was backed by the prime minister, as talk of international reconciliation was left to junior ministerial ranks.

Boris Johnson went further. The war was the fault of German expansionism and aggression, London's mayor pronounced, and called for Labour's shadow education secretary Tristram Hunt to be sacked forthwith if he doubted it. The Conservative grandees were backed up by a retinue of more-or-less loyal historians. Max Hastings reckoned it had been fought in defence of "international law" and small nations, while Antony Beevor took aim at "anti-militarists".

This is all preposterous nonsense. Unlike the second world war, the bloodbath of 1914-18 was not a just war. It was a savage industrial slaughter perpetrated by a gang of predatory imperial powers, locked in a deadly struggle to capture and carve up territories, markets and resources.

Germany was the rising industrial power and colonial Johnny-come-lately of the time, seeking its place in the sun from the British and French empires. The war erupted directly from the fight for imperial dominance in the Balkans, as Austria-Hungary and Russia scrapped for the pickings from the crumbling Ottoman empire. All the ruling elites of Europe, tied together in a deathly quadrille of unstable alliances, shared the blame for the murderous barbarism they oversaw. The idea that Britain and its allies were defending liberal democracy, let alone international law or the rights of small nations, is simply absurd.

It's not just that 40% of men and all women in Britain were denied the vote in 1914 – unlike Germany, which already had full male suffrage – or that the British empire was allied with the brutal autocracy of tsarist Russia.

Every single one of the main warring states was involved in the violent suppression of the rights of nations throughout the racist tyrannies that were their colonial empires. In the decades before 1914, about 30 million people died from famine as colonial officials enforced the export of food in British-ruled India, slaughtered resisters in their tens of thousands and set up concentration camps in South Africa.

Britain was supposed to have gone to war to defend the neutrality of "plucky little Belgium" – which had itself presided over the death of 10 million Congolese from forced labour and mass murder in the previous couple of decades. German colonialists had carried out systematic genocide in what is now Namibia in the same period.

As to international law, Britain's disdain for it was demonstrated when Germany had asked by what right it claimed territory in Africa a few years before. London refused to reply. The answer was obvious: brute force. This was the "liberal" global order for which, in the words of the war poet Wilfred Owen, the ruling classes "slew half the seed of Europe, one by one".

In reality, it wasn't just the seed of Europe they sacrificed, but hundreds of thousands of troops from their colonies as well. And in case there were any doubt that all the main combatants were in the land-grabbing expansion game, Britain and France then divvied up the defeated German and Ottoman empires between them, from Palestine to Cameroon, without a thought for small nations' rights, laying the ground for future disasters in the process.

Gove and his fellow war apologists worry that satirical shows such as Blackadder have sapped patriotism by portraying the war as "a series of catastrophic mistakes perpetrated by an out-of-touch elite". The incompetence and cynicism of generals and politicians certainly had horrific results. But it was the nature of the war itself that was most depraved.

Fortunately, the revisionists lost the argument among the public long ago – just as Gove has largely lost his battle to impose a tub-thumping imperial agenda on the school history curriculum. They will keep trying though, because history wars are about the future as much as the past – and so long as imperial conflict is discredited, future foreign military interventions and occupations will be difficult to sell.

For the rest of us, this year's anniversary should be a reminder that empire in all its forms, militarism and national chauvinism lead to bloodshed and disaster. It also contains a warning about the threat from the rise and fall of great powers. China is no imperial Germany, but the US – allied with Japan – is a declining global power in a region in which it is tightening its military grip. It's not 1914, but the dangers are clear.

Twitter: @seumasmilne

• This article was amended on 14 January 2014. It originally stated that in 1914, most men did not have the vote. This has now been corrected.