On the morning of 18 August 1918, units of the Belgian army climbed out of their trenches and advanced. For the first time since the invasion of their country four years earlier, they drove the Germans back, and in doing so took the hamlet of De Kuiper. It was not recognisable any more as a place where anyone had ever lived, simply a desolate wasteland of mud and craters, but it was, nonetheless, Belgian land, their land. It was for Belgians a small but symbolic victory, a proud victory.

Back home in Radlett, Hertfordshire, my grandfather, Emile Cammaerts, heard the glad news and rejoiced. He was a fiercely patriotic Belgian poet – it could be said, the Rupert Brooke of the the Belgians – who, after the German invasion of his country, had written deeply felt and stirring poems, to summon up Belgian blood, to stiffen Belgian sinews. This poem of his, Le Drapeau Belge, like others he wrote, had been set to music by Edward Elgar and performed by Tita Brand, my actress grandmother.

Le Drapeau Belge

Rouge pour le sang des soldats

– Noir, jaune et rouge –

Noir pour les larmes des mères

– Noir, jaune et rouge

Et jaune pour la lumière

Et l'ardeur des prochains combats.

Au drapeau, mes enfants,

La patrie vous appelle,

Au drapeau, serrons les rangs,

Ceux qui meurent, vivent pour elle!

Other verses follow in much the same vein. But for my grandfather, that same date was the cause of yet more celebration, the birth of his daughter, my mother. To mark this happy coincidence, Emile named her Kippe, the slightly anglicised name of De Kuiper, now once more, triumphantly, in Belgian hands.

At home, as a small boy, for reasons still not entirely clear to me, we always called our mother, never mummy or mum, but Kippe. So that name, that place, that story, with all their associations to the first world war, became an integral part of my growing up.

One war, as we know, so often leads directly or indirectly, sooner or later, to the next. It seems to me to be self-evident that the Treaty of Versailles at the end of the first world war, the determination by the Allies to punish and humiliate the German people, the sufferings they endured after their defeat, the hunger, mass unemployment and then hyperinflation, was, at least in part, a cause of the rise, out of these bitter ashes, of fascism and Hitler, and of the next world war 20 years later.

Ten million men had died on all sides in the first world war, 20 million and more in the second, as well as the countless millions of civilians. Among the dead was one of Emile Cammaerts' sons, and my uncle, Pieter Cammaerts, an actor, a son, a brother, who was killed in the RAF in 1941, aged 21.

He is buried in a churchyard in Radlett alongside my grandparents. Born in 1943, I have no memory of him – he was simply a photo on a mantelpiece as I grew up, the only one of my relatives whose face has remained always unchanged for me. But the story of his short life and the story of my mother's name, I do remember. I know them well. And I know my grandfather's poetry too. They are a part of me now. It is not just genes that make us who we become, it is our stories too.

I learned young, as many of my generation did, of the significance of the red poppy, of Armistice Day, of Remembrance Sunday, the stories of sacrifice and valour. I aspired to be like them, like my uncle Pieter, brave in the face of terrible danger, and like my other uncle, Francis Cammaerts, who had been a pacifist at the outbreak of war, and who then, on learning of his brother's death, had become an SOE agent in France – to me, both heroes.

I wanted to live up to their example. But growing up in post-war England, I witnessed too, my mother's tears, the grieving for her brother that lasted all her life. In community and country I saw all around me the destruction wreaked by war, and came to understand slowly the effect of war on family and friends.

Eric Pearce, one such family friend, an ex RAF pilot, used to visit from time to time. His face and hands had been terribly burnt when his plane was shot down. I had gazed on his scars as a young child, fascinated, horrified. Those scars, and all the memories, left their scars on me.

Later, as a schoolboy and as a young man, I read the poems of Edward Thomas, Wilfred Owen, Siegfried Sassoon and others. I saw Journey's End, heard Britten's War Requie, read All Quiet on the Western Front, saw the films Paths of Glory and La Grande Illusion. I explored the history of the first world war, went to the Commonwealth war graves around Ypres and found myself, almost by accident, in the hamlet that bears my mother's name, almost, De Kuiper. Full circle. End of story. But it wasn't.

War Horse opened in London in 2007. Now it is performed in Berlin, the first play about the first world war to be staged there. Photograph: Graeme Robertson

This autumn, the National Theatre's iconic production of War Horse opened in Berlin. It is, I am told, the first play about the first world war to be put on there since the first world war began. In Der Theater dem Westens, the very same theatre where the kaiser sat, and Hitler too, there is being performed each night a play about peace and reconciliation, and about the pity of war too. Someone once called it "the greatest anthem to peace" ever seen on stage. So in 2014, a hundred years after the beginning of that holocaust of a war, the play will be on in London and Berlin.

An English play translated into German, it has a German cast, singing English folksongs in German, I was there on the first night in Berlin. It was a night to remember. A night I will never forget. For me it was the end of a long, long trail awinding from De Kuiper in 1918 to Berlin in 2014, through 70 years of stories, of history. But I know I have no memories as such of war. Remembrance of those times, of the people who suffered and died, may be deeply felt, and they are, but all of it has been passed on. I did not live the memories they lived.

The last of our soldiers of the first world war was Harry Patch. He died in July 2009. Of war he once said: "Too many died. War isn't worth one life … It's the calculated and condoned slaughter of human beings. All these young lives lost in a war which ended across a table. What's the sense in that?" Harry Patch saw it, lived through it, lived his memories every day. He was the last one who did.

Harry Patch, the last British survivor from the war who died in 2009. Photograph: Don McCullin/PA/MoD

Still living in my village of Iddesleigh in Devon is Dorothy Ellis, the last surviving widow of any soldier who fought in the first world war. She is now 93. Dorothy was married to Wilf. And thereby hangs a tale. He was one of three old men alive at the time of the first world war, and still living in Iddesleigh some 40 years ago when we first moved there.

I got to know Wilf, not well, but well enough to talk to. I met him by chance one day in the pub, The Duke of York. He was an antique dealer by now, a "knocker", and in his youth, after the first world war, had been a violinist in a dance orchestra on grand transatlantic liners. We got talking by the fire.

But that morning we didn't talk about transatlantic liners. We talked of his time as a soldier in the first world war. It wasn't a conversation for very long, but became a monologue quite soon.

He lived every word he spoke, smiling, laughing sometimes too, through his tears. There were long silences too, when he would sit staring into the fire. I knew better than to interrupt. He told me of his time in the trenches, of being gassed, of the horror and the fear, of the beast and the hero that war brings out in men, of the cold and the mud, of the camaraderie, of longing for home, for it all to be over.

He took me back to his home afterwards for a cup of tea, and showed me his trenching tool, photos of his pals, and some medals. Dorothy told me later that he had only rarely spoken about these experiences. I felt then, as I feel now, that Wilf was passing them on to me, telling me his story. This was no historian, he was not composing a poem, or making a play or film, he was simply telling me his memories, how it was to have been there.

So, not long afterwards, did another of the three old men of the village, Captain Budgett, squire and ex master of foxhounds. He had been there with horses, he told me. He spoke of his horse as his trusted friend, on whom his life depended, to whom he'd confide his worst fears, and his hopes too. "That horse listened," he said, "really listened."

And old Albert Weeks, too young to go to the war, told me how it was to see the farm horses sold off to the army on the village green, how the men marched away, and some of them he never saw again, how everyone thought things would be better after the war was won, how he supposed it was in a way, but then it wasn't, because there was another war soon after, wasn't there?

Subsequent research soon told me that about as many horses had died in the first world war as had men, and they had died the same way too: blown to pieces, machine-gunned, caught in the wire, drowned in the mud.

I decided I would tell the story of that war seen through the eyes of a horse. Joey, I would call him. It would be Wilf's story, Captain Budgett's story, Albert's story, an English story, but a German one too, and a French one. It would be a tale, as far as possible, of the universal suffering, not just in that war but in all wars, and on all sides. That is the spirit in which the book was written, and in which the play is acted out now each night, over in Berlin and in London, and on tour as it is in the US and the UK.

When Joey, lost in no man's land, is caught and trapped in the wire, his scream is the scream of all humanity crying out in agony and rage against the massacre and suffering of the innocent. And when Tommy meets Fritz later to free Joey from the wire, and shake hands, it is a moment of hope, a moment that reflects our longing for peace.

To tell the story is the only way we have left to remember, and the only way to pass it on. And it is important to pass it on, important for the men who died on all sides, all now unknown soldiers, for those who suffered long afterwards and grieved all their lives. And important for us too. If they gave their todays for our tomorrows, then, I am sure, after all they went through, and died for, they would wish to see us doing all we can to create a world of peace and goodwill, a world that one day will turn its back on war for good. It is through their words and our stories that we must and will remember this and remember them. Then we really will be honouring their memory.

In 2014, as we begin to mark the centenary of the first world war, we should honour those who died, most certainly, and gratefully too, but we should never glorify. We should heed the words of those who were there, who did the fighting, and some of them the dying. Wilf Ellis, Harry Patch, Sassoon, Thomas and Owen. Siegfried Sassoon wrote of "the callous complacency" of those back home who wished only to prolong the war, no matter what the cost. To Wilfred Owen, the words Horace had used to glorify war centuries before, "Dulce et decorum est pro patria mori" – how sweet and fitting it is to die for your country – were simply "the old lie".

During these next four years of commemoration we should read the poems, the stories, the history, the diaries, visit the cemeteries – German cemeteries as well as ours – they were all sons and brothers and lovers and husbands and fathers too.

There should be no flag waving, unless it be the lowering of the flags of all the nations who lost their sons, unless it be to celebrate the peace we now share together, unless it be to reaffirm again our determination to guard our freedom, but as far as humanly possible to do it in peace. And when we sing the anthems, let them be anthems of peace and reconciliation. Come each November over the next four years, let the red poppy and the white poppy be worn together to honour those who died, to keep our faith with them, to make of this world a place where freedom and peace can reign together.

This is from Only Remembered, by John Tams, the song that begins and ends the National Theatre's play of War Horse.

Only the truth that in life we have spoken

Only the seed that in life we have sown.

These shall pass onwards when we are forgotten,

Only remembered for what we have done.

Only remembered, only remembered, only remembered for what we have done.