Answer:
The United States decided to remain neutral during the Great War, which began in 1914 after the assassination of Archduke Franz Ferdinand of Austria-Hungary. This because they considered that it was a European conflict, which did not influence the commercial or political interests of America.
Now, after a series of diplomatic altercations with Germany, such as the Zimmermann Telegram and the sinking of the Lusitania, on April 6, 1917, America entered the war. Thus, 2 million American soldiers joined the allied forces, mainly British, French and Russian, who were fighting in the Old Continent. This new number of soldiers, without participation in previous combats, tipped the balance for the allied side, given that the forces of the Central Powers were already exhausted and without resupply capacity.
