The allied offensive began on that morning when 100,000 British soldiers rose out of their trenches and started to cross the no-mans-land that separated them from their German foes. In the days leading up to this offensive 250,000 shells had rained down on the German positions close to the Somme river, the British troops had expected the way forward to be clear for them.

Many of the German machine guns and gunners had survived the onslaught by the British artillery and the British infantrymen were massacred. By the end of that first day 20,000 British soldiers were dead and another 40,000 were wounded. It remains to this day the heaviest day of  casualties suffered in British military history.

After this disaster smaller advances were heavily fought over and despite this over 1,000 lives were lost for every 100 yards gained. British tanks entered into the battle on September 15 for the first time in history. Their introduction failed to break the deadlock in this stalemate of a battle and with the arrival of heavy rains in the October the battlefield resembled a sea of mud. After more than four months of slaughter Haig called off the offensive on November 18.

This offensive was a military disaster, it resulted in the British army and its allies gaining just 125 square miles taken from the German army at a very heavy cost. More than 600,000 British and French soldiers were killed, wounded, or missing in action. The German army fared even worse with more than 650,000 casualties. Haig was heavily criticized for the battle with his willingness to commit so many lives and resources to this stalemate, although actions like this did eventually contribute to the collapse of an exhausted German army in 1918.