World War I was fought primarily in Europe, along the Western Front that stretched from the English Channel south along the French border to the Alps, and on the Eastern Front across Poland, Galicia (the region encompassing part of Hungary and the Ukraine) and Russia. It was a “world” war, however, for two reasons. First, hundreds of thousands of troops from around the world fought in it, the most numerous of which were citizens of the British Empire drawn from as far away as India and New Zealand. Second, military engagements occurred in the Ottoman territories of the Middle East, in Africa between European colonial armies, and in Asia (albeit at a much smaller scale). Japan even supported the Entente war effort by taking a German-controlled Chinese port, Tsingtao.
The other major power involved in the war, the United States, was a latecomer to the fighting. The United States was dominated by "isolationist" sentiment until late in the war. Most Americans believed that the war was a European affair that should not involve American troops. America, however, was an ally of Britain and provided both military and civilian supplies to the British, along with large amounts of low-interest loans to keep the British economy afloat. In 1917, as the war dragged on and the German military leadership under the Field Marshal Paul Von Hindenburg recognized that the nation could not sustain the war much longer, the German generals decided to use their new submarines, the U-Boats, to attack any vessel suspected of carrying military supplies to the British or French. When ships carrying American civilians were sunk in 1917 (especially the Lusitania, a passenger vessel carrying over 1,000 people, including many Americans), American public sentiment finally shifted and the US declared war on Germany in April of 1917.
The importance of the entrance of the United States in the war was not the superiority of American troops or technology - American soldiers were as horrified as anyone when they first encountered modern, mechanized warfare. Instead, the key factor was that the US had a gigantic industrial capacity, dwarfing all of the great powers of Europe put together, and millions of fresh troops that could be called up or drafted. Germany, meanwhile, had been totally committed to the war for almost three years, and its supplies (of money, fuel, munitions, food, and people) were running very thin. Most German civilians still believed that Germany was winning, but as the carnage continued on the Western Front, the German general staff knew that they had to achieve a strategic breakthrough.
By 1918, it was clear to the German command that they were losing. They had been able to fight the French and British to a standstill on the Western Front, but when the US entered on the side of the British and French, it became impossible to sustain the war. The only hope appeared to be one last desperate offensive that might bring the French and British to the negotiating table. Thus, German forces staged a major campaign in the spring of 1918 that succeeded in breaking through the western lines and coming within about 40 miles of Paris, but by then German troops had outpaced their supply lines, lost cover, and were now up against the combined reserves of the French, British, and Americans. Another attempted offensive in July failed, and the Entente (and American) powers began to push the German forces back.
Back in Germany, criticism of the Kaiser appeared for the first time in the mainstream press, and hundreds of thousands of workers protested the worsening economic conditions. In late September, the head of the German General Staff, Ludendorff, advised the Kaiser to sue for peace. A month later, the Reichstag passed laws making the government’s ministers responsible to it instead of the Kaiser. Protest movements spread across Germany and the rapidly-collapsing Austro-Hungarian empire, as nationalist movements declared independence in Yugoslavia, Hungary, Czechoslovakia, and the Balkans.
On November 11 of 1918, a voluntary commission of German politicians led by the German Socialist Party (SPD) formally sued for peace. The Kaiser, blaming socialists and Jews for "stabbing Germany in the back," snuck away in a train to Holland, where he abdicated. The top generals of the German General Staff, Hindenburg and Ludendorff, themselves the authors of the myth of the “stab in the back,” did their best to popularize the idea that Germany “would have won” if not for sabotage perpetrated by a sinister conspiracy of foreign agents, communists, and (as with practically every shadowy conspiracy theory of the twentieth century) Jews. In fact, if the commision of German politicians had not sued for peace when they did, French, British, and American troops would have simply invaded Germany and even more people would have died.