The death of innocence in the Battle of the Somme, but what have we learned a century on?

They walked unflinching to their deaths across the muddy, pitted landscape into the machine guns and the intact lines of barbed wire

At 7.30am on July 1st 1916, they rose from the trenches, line after line of them, all abreast, each man about an arm’s length from his neighbour. And walked, because they had been ordered to walk, unflinching to their deaths across the muddy, pitted landscape into the machine guns and the intact lines of barbed wire on which so many would be fatally impaled.

19,240 of them died that first day of the battle of the Somme; the worst day of the worst battle in human history. By its end, 140 days later, one million would have died, been lost, or wounded in the battle that came to represent the apotheosis of a new form of warfare and industrial slaughter, and ultimately of the folly and extraordinary capacity for self-destruction of mankind.

We have a particular duty to remember and honour the 2,000 dead that day of the 36th Ulster Division. And the 599 dead of the Tyneside Irish who marched into battle behind the regimental piper playing The Minstrel Boy. And the countless other Irishmen who fought and died in other British regiments on the Somme, memories of whom are still interwoven, North and South, in the complicated personal and community narratives that combine to make us what we are.

No one tradition or story is diminished or undermined by the remembering of the extraordinary self-sacrifice and courage of so many that day, or by what President Higgins has called the "narrative hospitality" that must be at the core of this inclusive decade of commemoration. More than men died there. "Idealism perished on the Somme," historian AJP Taylor wrote. And "Innocence," Philip Larkin noted. But have we learned?