The German Spring offensive
In March 1918 the Germans launched their final offensive of the war. They knew it was their last chance to win because America had declared war on Germany in April 1917. American troops were arriving in France at the rate of 300,000 a month. At first the offensive was a remarkable success but the troops were now tired and hungry and, eventually, they were stopped, just 40 miles from Paris.
The British, French and American forces launched a huge counter-attack against the exhausted German army in August 1918. The Austrians were also under pressure and simply gave up after a heavy defeat by Italy at the end of October. The Germans were driven back and by November 11 1918, when Germany agreed to stop the war, they had retreated as much as 120 kilometres. During the battle of the Somme in 1916 it took the British five months of fighting to advance just eight kilometres.
Neil Demarco: Britain and the Great War; Oxford University Press, 1992/2000, page 15