IT was the most terrible day in the history of the British Army with more than 57,000 casualties, of whom almost 20,000 were killed.
But the first day of the Battle of the Somme - July 1, 1916 - was just the beginning of a four-month operation that would end with more than 1.5m casualties.
The shattered fields of northern France ran red with blood and to this day the countries that took part remember the events with abject horror.
The pictures were taken entirely unofficially by Bridlington-born Lieutenant John Stanley Purvis - who was risking a court martial by doing so.
He and his men, of the 5th (T) Battalion The Yorkshire Regiment (Green Howards), were in the second line of trenches and watched as the first wave went over the top.
One of his pictures shows the advance of men in the forward trenches, another is a general view of the battlefield and a third the moment a shell explodes nearby.
Another is an image of two men ready in the trench with their rifles, at the entrance to a tunnel that ran under No Man’s Land.
Lt Purvis was one of the lucky ones. He survived the war, taught classics after a Cambridge education and was then ordained in the church. He served as a vicar in York and Old Malton among other places.
Eventually he became a Canon of York Minster and played a major role in the founding of the city’s Borthwick Institute of Historical Research, now part of York University. He died in 1968.
His pictures have now joined hundreds of others on the Green Howards Museum’s website as part of a Lottery-funded project to scan and upload as many images as possible.
Museum director Lynda Powell said: "It is amazing that a young lieutenant on the Front in 1916 had both the desire and the camera to take pictures at a time when his life must have been in imminent danger."
The photographic collection can be found by visiting greenhowards.org.uk and following the links to the museum.