They were the battlefields where thousands of young New Zealand men were slaughtered.

Among the headstones of those who never returned home, hundreds gathered in the tiny town of Longueval, in northern France.

It was here that at 6.01am on September 15, 1916, thousands of New Zealand ground troops entered the Battle of the Somme on the Western Front of World War I.

A member of the Maori Cultural Group arrives at the ceremony to commemorate the 100th anniversary of the Battle of the Somme. Photo / AP
A member of the Maori Cultural Group arrives at the ceremony to commemorate the 100th anniversary of the Battle of the Somme. Photo / AP

Before a month had elapsed some 15,000 Kiwis had entered the fray. More than 2000 died and another 6000 were injured.

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The nearest approach to hell imaginable.

Under a sky streaked with pink in the flush of dawn they retraced the final steps marched by many of the New Zealand soldiers slaughtered on the first day of battle.

"A new battlefield has a smell very hard to explain," wrote one unidentified Kiwi soldier in the first days on the Somme.

"High explosives ... Gasses, mixed with rotting corpses. A rotten egg being rammed down one's throat may come near it. If the civilian police could bottle the smell it would be a great thing for breaking up riots.

"A wild screech, a crash ... The mud was our saviour. We were plastered with it. I had a piece of mud the size of my two fists ... My tongue and lips were dry. Had the ground been hard we would have been blown to pieces.

"A corporal from another battery had been killed during the night. The body is lying on the road. The ammunition wagons are running over him.

"This particular bit of road is under direct observation and we do it at a gallop. It would be suicide for us to stop to remove the body ... (four days later) he is still where he fell.

"Going in this afternoon, the wheels went right down his backbone, the head became adrift from the body and was pushed out of sight in the mud. Another New Zealander who will be reported missing, believed killed in action."

Details in the diary entry - read at dawn by New Zealand Returned Services Association vice president Bob Hill - might be confronting, but to understand the sacrifice they need to be known.

"I must admit when I was first given [the entries] to read I thought 'goodness gracious'. It's so hard to think back and put yourself in their place," Mr Hill said.

"All the readings said it the way it was and not the way some people might like to hear it. It was graphic but it was true.

"I served in Borneo and Vietnam and even that compared to what these people put up with, it's chalk and cheese.

"We need to know just what these people put up with and the sacrifices they made before we can move on."

At the Caterpillar Valley Cemetery people sat among the headstones of the soldiers they were there to remember, including the 1200 New Zealand men commemorated at the cemetery whose graves are unknown.

Children too young to understand the significance of the day bounded between the rows of graves playing cheerfully as those who fought 100 years ago for their freedom were remembered for their boundless courage and tenacity.

Two historic military planes flew overhead, dropping hundreds of poppies into the cool morning breeze.

Britain's Prince Charles delivers his speech during the ceremony commemorating the 100th anniversary of the Battle of the Somme. Photo / AP
Britain's Prince Charles delivers his speech during the ceremony commemorating the 100th anniversary of the Battle of the Somme. Photo / AP

"Standing in this peaceful scene today it is hard to imagine that a century ago this was an infernal blasted wasteland," said Prince Charles, dressed in full New Zealand military garb.

"We are gathered here today to honour New Zealand's role in the Battle of the Somme. That calamitous engagement represented what was, for a new nation, the greatest loss of life it had experienced in one day, only to be exceeded the following year [at Passchendaele].

"None came further to serve here than the New Zealanders, who, on the Somme, confirmed their reputation as exceptional soldiers. They engaged with boundless courage and tenacity in defence of values of liberty that we still hold dear to this day.

"What occurred here 100 years ago did not create national character, it revealed it."

Three years ago Rebecca Nelson was busking in Devonport when she was scouted by the Navy.

Yesterday she was the voice of a nation.

In a cloak weaved of New Zealand bird feathers, the able musician brought tears to the eyes of those listening to her sing anthems and hymns.

Rebecca Nelson sings the New Zealand and French national anthems at the dawn service to commemorate 100 years after New Zealand troops entered the Battle of the Somme

Posted by nzherald.co.nz on Wednesday, 14 September 2016

"When I sing I sing for us, but I also sing for the ones who aren't here and I just look out and go 'this is for you'," she said.

By dusk, light rain had brought a chill over the Somme after a week of scorching temperatures.

"Our day (marking the centenary) has been quiet, orderly and contemplative, so unlike the hell endured here by my countrymen 100 years ago," said defence chief Lieutenant-General Tim Keating.

"We will soon return to our comfortable homes or hotels and a good night's sleep. The exhausted New Zealanders who had survived the battle ... craved with a desperation that few, if any, of us assembled here have ever experienced, to sleep, to rest.

"After the New Zealanders were withdrawn from the Somme, Field Marshal Sir Douglas Haig sent a message to New Zealand that the New Zealand Division had fought with the very greatest gallantry in the Somme battle for 23 consecutive days, carrying out with complete success every task set and always doing more than what was asked of them. The division won universal confidence and admiration. No praise can be too high for such troops.

"Such words may have been of some comfort to the survivors and the families of those who had given their all in the Somme. But no words can properly address the burden of memory that the men who left here carried with them for the rest of their lives."

After the sun disappeared below the horizon many were already back in Longueval as members of the New Zealand Defence Force returned to surround the battlefield memorial.

Barely illuminated by the cenotaph's haunting yellow lights they performed a haka on the spot where thousands of soldiers were killed 100 years earlier.

A piece of music named A Day In Battle retold the tragedy faced by those brave young men.

Bugle calls directed troops; a whistle sounded and snare drums erupted to depict the gunfire that bombarded the men from all angles.

People stand during a ceremony to commemorate the 100th anniversary of the Battle of the Somme in the New Zealand Battlefield Memorial in Longueval, northern France. Photo / AP
People stand during a ceremony to commemorate the 100th anniversary of the Battle of the Somme in the New Zealand Battlefield Memorial in Longueval, northern France. Photo / AP

When finally the guns fell silent, the smoke lifted to reveal casualties on both sides.

Surviving troops were summoned home, where they marched with heads low and exhausted.

The sporadic beats of a single bass drum depicted a heart slowly taking its last beat. The price of peace was high and thousands of men were left behind, but they will never be forgotten.