The Battle of the Somme: Why is this battle significant in British military history? What were the results?

One hundred and twenty-five miles northwest of Verdun, the British and French armies joined at the Somme River. A Franco-British offensive was planned here for 1916 to relieve pressure on the French at Verdun. British General Douglas Haig ordered a massive bombardment of the German lines that would last a week and could be heard across the Channel in England. But the German troops were deeply dug in and the bombardment did not reach them. Once the shelling was over, of the 100,000 British troops who attacked the German lines July 1, 1916, 20,000 were killed and over 40,000 were wounded. It was the single worst day in deaths and casualties in British military history. Eventually this battle, which did not change the front line trenches much at all, involved over 2 million men along a 30 mile front. British and French losses numbered nearly three-quarters of a million men.