Somme tragedy - biggest loss of lives in a single day of fighting
The Battle of the Somme took place near the Somme River in France, and lasted from July 1, 1916, to November 18 that year.
It saw the biggest loss of soldiers' lives in a single day of fighting ever recorded by the British army.
The battle was between the British and French, on one side, and the German Empire, on the other, and it symbolised the horrors of the First World War.
With both sides engaged in trench warfare with little movement, the British and French were organising a major attack at the Somme,determined to break the stalemate.
When the Germans went on the offensive and attacked the French at the Battle of Verdun in the east of Paris, the British attack at the Somme was brought forward in the hope the Germans would move some of their men away from Verdun.
At the Battle of the Somme, there was a week-long artillery bombardment of the German lines, which saw the British firing more than 1.6m shells. The reason behind all that artillery was to destroy the German trenches and to try and kill most of the German soldiers.
After all the firing, British and French soldiers came out of their trenches and walked towards the German lines, believing they would not face much opposition.
German soldiers, though, had been hiding in special shelters and had waited underground for a week until the shelling had finished, then came out to fire machine guns at the advancing Allied troops.
Irish, English, Scottish and Welsh soldiers were gunned down, along with French, Australians and South Africans. One of the few units to meet their objectives that day was the 36th Ulster Division, which showed remarkable bravery and sacrifice and which is forever remembered by the people of Northern Ireland.
The 36th Ulster Division took a German fortification called the Schwaben Redoubt before a lack of re-enforcements forced them to retreat.
The division was relieved on July 2, having suffered more than 5,000 casualties - with more than 2,000 of those killed. Several Victoria Crosses were awarded to the Ulster Division for their courage.
The mainly Catholic 16th Irish Division were separated from their comrades in the 36th Ulster Division by only a few months. On September 3, another great British offensive went in. The men of the 16th Division fought with the same courage as the 36th Division. Within 10 days the division had lost half of its 11,000 men through death or injury.
Two Victoria Crosses were awarded, one to a private in the Connaught Rangers and one to a young officer in the Leinsters.
The Battle of the Somme ended with the British having advanced only five miles.
It is thought the British suffered 420,000 casualties, including nearly 60,000, on the first day alone. The French lost 200,000 men and the Germans nearly 500,000.