After more than two and a half years of efforts by President Woodrow Wilson to keep the United States out of the war, America formally declared war on Germany on the 6th April 1917. Apart from an Anglophile element urging support for the British, American public opinion went along with neutrality at first: the sentiment for neutrality was particularly strong among Irish Americans, German Americans and Scandinavian Americans, as well as among church leaders and women. On the other hand, even before World War I had broken out, American opinion had been more negative toward Germany than towards any other country in Europe. Over time, especially after reports of atrocities in Belgium in 1914 and following the sinking of the passenger liner RMS Lusitania in 1915, the American people increasingly came to see Germany as the aggressor in Europe.
As U.S. President, it was Wilson who made the key policy decisions over foreign affairs: while the country was at peace, the domestic economy ran on a laissez-faire basis, with American banks making huge loans to Britain and France — funds that were in large part used to buy munitions, raw materials and food from across the Atlantic. Until 1917, Wilson made minimal preparations for a land war and kept the United States Army on a small peacetime footing, despite increasing demands for enhanced preparedness. He did however expand the United States Navy.
In 1917, with Russia experiencing political upheaval following widespread disillusionment there over the war, and with Britain and France low on credit, Germany appeared to have the upper hand in Europe, while her Ottoman ally clung stubbornly to her possessions in the Middle East. In the same year, Germany decided to resume unrestricted submarine warfare against any vessel approaching British waters; this attempt to starve Britain into surrender was balanced against the knowledge that it would almost certainly bring the United States into the war. Germany also made a secret offer to help Mexico regain territories lost in the Mexican–American War in an encoded telegram known as the Zimmermann Telegram, which was intercepted by British Intelligence. Publication of that communique outraged Americans just as German U-boats started sinking American merchant ships in the North Atlantic. Wilson then asked Congress for “a war to end all wars” that would “make the world safe for democracy”, and Congress voted to declare war on Germany on April 6, 1917 (though it did not declare war on Austria-Hungary until 8 months later on December 7, 1917.
U.S. President Woodrow Wilson initially planned to give command of the AEF (American Expeditionary Force) to Gen. Frederick Funston, but after Funston’s sudden death, Wilson appointed Major General John J. “Black Jack” Pershing in May 1917; Pershing remained in command for the entire war. Pershing insisted that American soldiers be well-trained before going to Europe and as a result, few troops arrived before 1918. In addition, Pershing insisted that the American force would not be used merely to fill gaps in the French and British armies, and he resisted European efforts to have U.S. troops deployed as individual replacements in decimated Allied units.
This attitude was not always well received by the Allied leaders who distrusted the potential of an army lacking experience in large-scale warfare. In addition the British tried to bargain their spare shipping to make the US put its soldiers into British ranks.
By June 1917, only 14,000 U.S. soldiers had arrived in France and the AEF had only a minor participation at the front in late October 1917, but by May 1918 over one million U.S. troops were stationed in France; though only half of it made it to the front lines. Since the transport ships needed to bring American troops to Europe were scarce at the beginning, the army pressed into service passenger liners, seized German ships, and borrowed Allied ships to transport American soldiers from New York, New Jersey, and Newport News, Virginia. The mobilization effort taxed the American military to the limit and required new organizational strategies and command structures to transport great numbers of troops and supplies quickly and efficiently. The French harbors of Bordeaux, La Pallice, Saint Nazaire and Brest became the entry points into the French railway system which brought the US forces and their supplies to the front. American engineers in France built 82 new ship berths, nearly 1,000 miles (1,600 km) of additional standard-gauge tracks and 100,000 miles (160,000 km) of telephone and telegraph lines.
The first American troops, who were often called “Doughboys”, landed in Europe in June 1917. However the AEF did not participate at the front until late October 1917, when the 1st Division fired the first American shell of the war toward German lines, although they participated only on a small scale. A formation of regular soldiers and the first division to arrive in France, entered the trenches near Nancy.
The AEF used French and British equipment. Pershing established facilities in France to train new arrivals with their new weapons. By the end of 1917 four divisions were deployed in a large training area near Verdun: the 1st Division, a regular army formation; the 26th Division, a National Guard formation; the 2nd Division, a combined formation of regular troops and United States Marines; and the 42nd “Rainbow” Division, a National Guard formation consisting of units from nearly every state in the United States. A fifth division, the 41st Division, had been converted into a depot division near Tours.