In 1914 Britain began blockading German ports in the hope that their starving and lack of war supplies may lead them to surrender. Both German civilians and soldiers suffered. In 1915 one third of all the pigs in Germany had to be slaughtered due to lack of fodder to feed them with. German people became very ill due to malnourishment leading to diseases like scurvy, influenza, dysentery and tuberculosis and 300,000 of them died. The winter of 1917-18 was called the Turnip Winter in Germany, as this is all there was left to eat. Morale among both troops and civilians was very low causing poor defending and attacking in the trenches as people began to lose faith in the war, most of the food went to the soldiers and the starving civilians criticized them and jeered at them demanding an end to war. Germany no longer had a sufficient chance in fighting.
In 1917 Russia left the war and bought some relief and confidence to the German soldiers, now they could fully concentrate on defeating Britain and France on the western front. However, not long after still in 1917 the USA joined the war following the sinking of their ships by German U-boats and the Germans attempt to persuade Mexico to go to war with the rest of America, revealed in the intercepted Zimmermann Telegram of 1917. By summer 1918 the Americans were bringing in 50,000 new, unharmed men each month along with new advanced weapons such as better-controlled tanks and more accurate machine guns. German morale was crushed; they were now largely outnumbered, fighting a war on two fronts and starving due to the British blockade of German ports. Allied morale was raised as now they were able to fight more effectively, however, by late 1917 Russia had become a communist country and reconciled with Germany so troops were withdrawn from the east, balancing out the numbers on either side of the battlefield. Despite this the Allies were still at an advantage and now even closer to winning the war.
Before the American forces had gathered in great numbers Germany launched one last shot at winning the war, the German offensive, or spring offensive of 1918 began with heavy bombardments and gas attacks followed by specially trained storm troopers who would move forward and infiltrate the Allied defences at previously identified weak points. This plan was intended to stop the allies from gathering their defence in one place. Germany managed to break enemy lines and advance 64 kilometres to Paris but lost 400,00 men in the process, 400,000 men that could no longer be replaced. Germany did not advance at all between the months of August and May due to being badly equipped and malnourished leading to bad discipline, trench warfare had now ended but Germany did not benefit from this.
On the other hand, the Allies under Commander Ferdinand Foch were thriving; they were well fed and had new tanks, aircraft and artillery. 456 tanks some of which were provided by the US were used against the Germans on August 8th 1918, named a “black day” for the German army. Germany was quickly losing and by late September the allies had reached the Hindenburg Line, a vast system of German defences in northeastern France. The US soldiers played a crucial part in this. The German Kaiser Wilhelm II fled to Holland when he realised Germany had no chance of winning the war, the army leadership called for an armistice.
To conclude I feel that although there were many reasons as to why the stalemate ended the involvement of the USA was a major turning point. This is because without the support from America British troops would not have been as well fed and the Allies would not have possessed as many new technologies and soldiers.