ON FEBRUARY 15 2003, well over a million people marched through London to oppose the intended invasion of Iraq. It was the biggest ever demonstration in British history. Six hundred other demonstrations took place all around the world, on every continent, including Antarctica.

They all knew why they were marching and by sheer force of numbers turned media and popular opinion around from the government’s intended story that somehow Iraq presented a threat to us all and that only by bombing could we secure the peace of the region, and indeed the world.

More than a decade later, billions spent, hundreds of thousands dead and more wars than ever, the sheer futility of war and its waste is there for all to see. The victims lie dead in unmarked graves amid the rubble, or the soldiers from the West are in heroes’ graves, in well-tended cemeteries, but still dead in their youth.

As Europe goes through a strange paroxysm of mawkish memorial of the Great War and a nasty dose of xenophobic, inward-looking behaviour, we need to learn from history of those who tried to stop that war and tried to point out where it could lead.

In my borough of Islington, north London, we have put up a memorial plaque at the end of every street where any WWI soldiers who lost their lives once lived. It is poignant to see the names of families where all sons perished in the war and, in a close-knit community, the way in which extended families were devastated by the carnage of the western front.

There has also been a good discussion of the anti-war movement. In my area many of the schools have undertaken studies. I was struck by a primary school’s piece of research into the life of Fenner Brockway, who was jailed and brutally treated as a conscientious objector and later went on to become a Labour MP in the forefront of the anti-imperialist movements of Britain and many other countries.

His story had been put up on a tree on Highbury Fields. The children who produced this saw his life as heroic, in the same way as soldiers who died in battle were seen as heroic. This simple piece of research by bright 11-year-olds opens a whole narrative as to what is history, who is heroic and who leaves a legacy.

Around them there are other legacies, including a pub named The Charlotte Despard, in honour of a great Suffragette, anti-war campaigner and Irish nationalist, who was also the sister of Sir John French, the first commander of the forces in Europe and later governor-general of Ireland where he brutally used the Black and Tans to suppress the thirst for liberty and independence.

Nearby is Keir Hardie House, a very well-built construction of good-quality council homes and named in his honour by the council who built the estate.

Hardie’s life, impressive by any standards, had a universal and global vision that was very different from many other great labour figures of the pre-1914 period.

It seems astonishing, at this distance, that on August 2 1914, two days before war was declared, he spoke in Trafalgar Square at a rally organised by the Labour Party (although initially called by the Daily Herald) where a declaration was adopted, which concluded by stating: “Men and women of Britain, you now have an unexampled opportunity of showing your power, rendering magnificent service to humanity and to the world. Proclaim for you that the days of plunder and butchery have gone by. Send messages of peace and fraternity to your fellows who have less liberty than you.

“Down with class rule. Down with the rule of brute force. Down with the war, up with the peaceful rule of the people!”

War, however, was declared and the Labour Party soon split between those who opposed it and those who decided to support the national endeavour of war and later joined the coalition government which introduced conscription and food rationing.

Hardie always opposed the war and stuck to the principles of the Trafalgar Square manifesto. He made his position crystal clear on the day Sir Edward Grey, the foreign secretary, came to Parliament to announce the start of the war.

Hardie was mocked by some of his fellow Labour MPs, who hummed the national anthem as he addressed the House of Commons chamber.

Eighty-nine years later, Labour prime minister Tony Blair told Parliament that there was no alternative to going to war with Iraq even after he and foreign secretary Jack Straw had failed to gain a second UN resolution specifically authorising war.

Interestingly, the debate focused very much on the legality of war. While this was not something so prevalent in the opposition to WWI, Hardie did frequently invoke the Hague Conventions as a way in which the war could have been avoided.

The evening before, in the most dramatic resignation speech of all time, the late Robin Cook told Parliament why he could not support the Iraq war: “Nothing could better demonstrate that they are wrong [commentators who claimed that Parliament was irrelevant to political decision-making] than for this House to stop the commitment of troops in a war that has neither international agreement nor diplomatic support.

“I intend to join those tomorrow night who will vote against military action now.”

The legacy of Hardie, and indeed the contradictions in the Labour Party between the ideal of national war as the supreme form of patriotism, and the wider global tradition of peace and fraternity, is still there and self-evidently not resolved.

Hardie and the ILP leadership continued their opposition to the war. As months, then years rolled on, jingoism and patriotism took over and they became more isolated. Conscientious objectors suffered appalling privations in jail or, as non-combatant stretcher bearers, died in enormous numbers.

For all the popular history of the supposed near-universal approval of WWI, it is remarkable how many of the war’s opponents were elected to councils and Parliament in the 1920s.

Parallels at a century’s distance are always difficult but the millions who marched against the Iraq war in 2003 have not recanted or recoiled from the position they held. Rather, many Labour MPs who supported the war lost their seats in 2005 and 2010 and in some cases issued abject apologies for their vote.

Somewhere in the midst of a century of wars and colonialism the tradition of real international solidarity has survived and now lives in a new generation in a very different world.

Or, looked at another way, is it so different?

• What Would Keir Hardie Say? is published by Luath Press, price £9.99.