The United States entered World War I in April 1917 with a small and unprepared army of only 200,000 soldiers. Trench warfare along the Western Front in Belgium and France had resulted in a stalemate, as both sides were dug into elaborate trench systems and employing new technologies like machine guns, barbed wire, artillery, and gas to attack the other side without much territorial gain. Over 4.5 million American men and 11,000 women eventually served, with 400,000 African American soldiers also called to duty. The newly arriving American troops played a critical role in helping turn the tide of a German offensive near Paris in spring 1918. By November 11, 1918, Germany agreed to an armistice, ending the war