As both sides dug in to their trenches, World War I became gigantic siege between the two sides.
At Verdun, the Germans were "bleeding the French army to death". The German Commander in Chief, Erich von Falkenhayn, had selected Verdun, believing that the French would be prepared to sacrifice their entire army, if necessary, to retain a position of such vital strategic importance. Von Falkenhayn considered it likely that the defeat of the French would cause the British army to collapse.
The German attack started on 21 February 1916 with 9 hours of bombing, and the battle raged on, with huge losses on both sides, and no end in sight. The commanders of the French army requested their British Allies to relieve Verdun and the commanders of the British and French armies, Sir Douglas Haig and Marshall Joffre, decided to open a second front, on the banks of the Somme river, to the west.
For six days, at the end of June, the Allied guns rained the German trenches with more than 1.6 million shells. It was the heaviest artillery bombardment in history.
Just before 7:30 AM, on July 1, 1916 the British fired two huge mines containing 200,000 lbs of high explosives. These were heard as far away as London and tore huge holes in the German trenches.
Confident that this punishment would have demoralised and all but defeated the enemy, the British Army left its trenches and went 'over the top'. The British commander, Sir Henry Rawlinson, was so certain there would be no German resistance he ordered his troops to march forward in parade formation, rather than tire themselves running across ground torn up with shellfire. Once the German lines were overcome, the British thought, Imperial cavalry divisions would chase the routed Hun back to the Rhine.
The Germans, however, were neither dead nor demoralised. They had waited out the bombardment in concrete bunkers. They surfaced, set up their machine guns on platforms they had ready prepared, and fired into the massed ranks of the approaching British Army, mowing down entire battalions and companies. Rawlinson, horrified by the German response, considered calling off the assault. Haig demanded that it be continued.
On the first day of the Somme, the British casualties were 19,240 dead, 35,494 seriously wounded, and 2,152 missing: 57,470 in total. French casualties, as they attacked on the left, were lighter, and they took a few German trenches, but as the British attack failed, they were forced to fall back.
The slaughter on the Somme went on for four more months as Haig refused to accept defeat. In the end, the Allies gained 125 square miles of ground from the Germans at the cost of 400,000 British and 200,000 French lives. The Germans suffered 450,000 casualties.
The battle of Verdun, which had continued on a smaller scale throughout the Somme, claimed 1.2 million lives in total, with the Germans finally pushed back in December 1916.