Although the United States played an important role in securing victory for the Allies in 1918, the country did not declare war on Germany until 6 April 1917. Most Americans agreed with President Woodrow Wilson’s initial stance on neutrality, although pro-Allied sentiment grew as the war progressed.
Within the United States, some members of the population – such as Irish-Americans – were hostile to helping Britain but there was less antipathy towards the French. France was America’s oldest ally and when German forces invaded northern France in 1914, some Americans believed it was vital that the United States join the war.