Alvin Cullum York (December 13, 1887 September 2, 1964), also known as Sergeant York, was one of the most decorated United States Army soldiers of World War I. He received the Medal of Honor for leading an attack on a German machine gun nest, gathering 35 machine guns, killing at least 25 enemy soldiers and capturing 132 prisoners. York's Medal of Honor action occurred during the United States-led portion of the Meuse-Argonne Offensive in France, which was intended to breach the Hindenburg line and force the Germans to surrender. He earned decorations from several allied countries during WWI, including France, Italy and Montenegro.

York was born in rural Tennessee, in what is now the community of Pall Mall in Fentress County. His parents farmed, and his father worked as a blacksmith. The eleven York children had minimal schooling because they helped provide for the family, including hunting, fishing, and working as laborers. After the death of his father, York assisted in caring for his younger siblings and found work as a blacksmith. Despite being a regular churchgoer, York also drank heavily and was prone to fistfights. After a 1914 conversion experience, he vowed to improve and became even more devoted to the Church of Christ in Christian Union. York was drafted during World War I; he initially claimed conscientious objector status on the grounds that his religious denomination forbade violence. Persuaded that his religion was not incompatible with military service, York joined the 82nd Division as an infantry private and went to France in 1918.

In October 1918, Private First Class (Acting Corporal) York was one of a group of seventeen soldiers assigned to infiltrate German lines and silence a machine gun position. After the American patrol had captured a large group of enemy soldiers, German small arms fire killed six Americans and wounded three. Several of the Americans returned fire while others guarded the prisoners. York and the other Americans attacked the machine gun position, killing several German soldiers. The German officer responsible for the machine gun position had emptied his pistol while firing at York but failed to hit him. This officer then offered to surrender and York accepted. York and his men marched back to their unit's command post with more than 130 prisoners. York was later promoted to sergeant and was awarded the Distinguished Service Cross. An investigation resulted in the upgrading of the award to the Medal of Honor. York's feat made him a national hero and international celebrity among allied nations.

After Armistice Day, a group of Tennessee businessmen purchased a farm for York, his new wife, and their growing family. He later formed a charitable foundation to improve educational opportunities for children in rural Tennessee. In the 1930s and 1940s, York worked as a project superintendent for the Civilian Conservation Corps and managed construction of the Byrd Lake reservoir at Cumberland Mountain State Park, after which he served for several years as park superintendent. A 1941 film about his World War I exploits, Sergeant York, was that year's highest-grossing film; Gary Cooper won the Academy Award for Best Actor for his portrayal of York, and the film was credited with enhancing American morale as the US mobilized for action in World War II. In his later years, York was confined to bed by health problems. He died in Nashville, Tennessee, in 1964 and was buried at Wolf River Cemetery in his hometown of Pall Mall, Tennessee.

World War I, often abbreviated as WWI or WW1, also known as the First World War and contemporaneously known as the Great War and by other names, was an international conflict that began on 28 July 1914 and ended on 11 November 1918. It involved much of Europe, as well as Russia, the United States and Turkey, and was also fought in the Middle East, Africa and parts of Asia. One of the deadliest conflicts in history, an estimated 9 million were killed in combat, while over 5 million civilians died from occupation, bombardment, hunger or disease. The genocides perpetrated by the Ottomans and the 1918 Spanish flu pandemic spread by the movement of combatants during the war caused many millions of additional deaths worldwide.In 1914, the Great Powers were divided into two opposing alliances: the Triple Entente, consisting of France, Russia, and Britain, and the Triple Alliance, made up of Germany, Austria-Hungary, and Italy. Tensions in the Balkans came to a head on 28 June 1914 following the assassination of Archduke Franz Ferdinand, the Austro-Hungarian heir, by Gavrilo Princip, a Bosnian Serb. Austria-Hungary blamed Serbia and the interlocking alliances involved the Powers in a series of diplomatic exchanges known as the July Crisis. On 28 July, Austria-Hungary declared war on Serbia; Russia came to Serbia's defence and by 4 August, the conflict had expanded to include Germany, France and Britain, along with their respective colonial empires. In November, the Ottoman Empire, Germany and Austria formed the Central Powers, while in April 1915, Italy joined Britain, France, Russia and Serbia as the Allied Powers.

Facing a war on two fronts, German strategy in 1914 was to defeat France, then shift its forces to the East and knock out Russia, commonly known as the Schlieffen Plan. This failed when their advance into France was halted at the Marne; by the end of 1914, the two sides faced each other along the Western Front, a continuous series of trench lines stretching from the Channel to Switzerland that changed little until 1917. By contrast, the Eastern Front was far more fluid, with Austria-Hungary and Russia gaining, then losing large swathes of territory. Other significant theatres included the Middle East, the Alpine Front and the Balkans, bringing Bulgaria, Romania and Greece into the war.

Shortages caused by the Allied naval blockade led Germany to initiate unrestricted submarine warfare in early 1917, bringing the previously neutral United States into the war on 6 April 1917. In Russia, the Bolsheviks seized power in the 1917 October Revolution and made peace in the March 1918 Treaty of Brest-Litovsk, freeing up large numbers of German troops. By transferring these to the Western Front, the German General Staff hoped to win a decisive victory before American reinforcements could impact the war, and launched the March 1918 German spring offensive. Despite initial success, it was soon halted by heavy casualties and ferocious defence; in August, the Allies launched the Hundred Days Offensive and although the German army continued to fight hard, it could no longer halt their advance.Towards the end of 1918, the Central Powers began to collapse; Bulgaria signed an Armistice on 29 September, followed by the Ottomans on 31 October, then Austria-Hungary on 3 November. Isolated, facing revolution at home and an army on the verge of mutiny, Kaiser Wilhelm abdicated on 9 November and the new German government signed the Armistice of 11 November 1918, bringing the fighting to a close. The 1919 Paris Peace Conference imposed various settlements on the defeated powers, the best known being the Treaty of Versailles. The dissolution of the Russian, German, Ottoman and Austro-Hungarian empires led to numerous uprisings and the creation of independent states, including Poland, Czechoslovakia and Yugoslavia. For reasons that are still debated, failure to manage the instability that resulted from this upheaval during the interwar period ended with the outbreak of World War II in 1939.