INCREASING AMERICAN SUPPORT FOR THE ALLIED POWERS
American sympathies and practical considerations dictated that American trade with the Allies increase as the war progressed. By 1916 American trade with the Central powers was down to near zero, whereas trade with the Allied powers had increased nearly 400 percent. Many who traded with Great Britain urged Washington to begin to prepare the United States for eventual war against Germany. A private National Security League was founded in late 1914 to instill patriotism in Americans and to psychologically prepare Americans for war. By the summer of 1915, Congress was taking the first steps to prepare the American army for actual combat in Europe. It should also be noted that peace movements existed in many major America cities, with women making up a large part of the membership of these organizations.
It was the actions of German U-boats that angered many Americans and caused them to favor entering the war against the “Hun.” According to existing international law, if one ship were to sink another, it first had to board the ship before sinking it and offer all on board “safe passage.” The advantage a U-boat had was that it glided underwater undetected and fired at other ships without warning.
Americans were outraged when a German U-boat sank a British passenger ship, the Lusitania, in the Atlantic Ocean on May 7, 1915; 128 Americans on board all perished. President Wilson issued a strong protest, but it should be noted that the ship was carrying weapons on it meant to help the Allied cause (which made it technically legal for the Germans to sink the ship). In addition, Germany had placed advertisements in major American newspapers warning Americans not to travel on the ship that day.
In August the Arabic, another passenger liner, was sunk by the Germans. President Wilson again forcefully protested; in response the Germans issued the “Arabic pledge,” in which they promised to stop sinking passenger ships without warning as long as the crews of the ships allowed the Germans to search the ships.
Official American concern about the actions of the U-boats continued. On March 24, 1916, a French ship called the Sussex was attacked by a U-boat; seven Americans on board were badly injured. The United States threatened to entirely cut diplomatic ties with Germany over this incident. In the Sussex Pledge the Germans promised to sink no more ships without prior warning. The actions described above all caused public opinion in the United States to increasingly favor military support of the Allied powers.