By August 6, when Austria declared war on Russia, all the members of the Triple Alliance and the Triple Entente had entered the war, with the exception of Italy, which declared neutrality. The Central Powers of Germany and Austria-Hungary stood against the Allies—Russia, France, Britain, and Serbia.
Japan came in on the side of the Allies late in August. Turkey joined the Austro-German side in November. After receiving competing territorial offers from both Allies and Central Powers, Italy joined the Allies in May 1915, and Portugal and Romania on the side of the Allies in 1916. In time much of the world joined in; there were fifty-six declarations of war before the end of 1918.
Americans had hoped to avoid entanglement in the European conflict, and for a time public opinion was deeply divided. While many Americans sided with Britain and France because they felt these two powers were fighting to assure that democratic government would survive in Europe, many others continued to think of Britain as the traditional enemy. Americans still thought of them- selves as upholding a tradition of isolation from wars that originated in Europe. To a considerable extent this was true, for no overseas invader had set foot on American soil since 1815. The American government committed itself quickly to a policy of neutrality.
As the war raged in Europe, however, public sympathies increasingly turned against the Central Powers, and against Germany in particular. Americans read of the war through British dispatches, heard atrocity stories that were directed against the Germans, and viewed the Habsburgs as attempting to suppress legitimate aspirations for the self-determination of peoples. Furthermore, the European war helped the United States economically, for Britain and France bought enormous quantities of goods from the United States. Within a year after the beginning of the war, the economies of the United States and the Allied powers were closely intertwined.
Still, the American business community had no reason to see the United States actively enter the war, for neutrality paid handsomely. President Woodrow Wilson (1856-1924) campaigned in 1916 on a pledge to keep the United States out of the conflict if possible. But he suspected that if German desperation over the flow of American foodstuffs to Britain were to continue, avoiding war would be very difficult. This proved to be so. American definitions of neutral shipping seemed to the Germans to openly favor the British.
Germany felt obliged to use its most powerful maritime weapon, the submarine, and in 1915 it proclaimed the waters around the British Isles to be a war zone in which enemy merchant ships would be sunk on sight. Neutral vessels entering the zone did so at their own risk. Americans insisted on exercising their rights on the high seas, including traveling on passenger vessels of combatants. On May 7, 1915, the British transatlantic steamer Lusitani a was sunk by a German submarine; 1,198 people died, including 124 Americans.
The United States protested in the strongest terms. Throughout 1915 German submarines complied, limiting their attacks to freighters. Nonetheless, further incidents followed, and in 1916 Germany formally agreed to abandon unlimited submarine warfare. Late that year Germany initiated peace efforts, but the Allies rebuffed these attempts.
Early in 1917 German military leaders gained the upper hand, and on February 1 submarine attacks on all neutral and belligerent shipping became official policy. Three days later an American naval vessel was sunk after warning, and Wilson asked Congress to sever diplomatic relations with Germany. Six more ships were sunk in the next month.
In the meantime, on March 12 a new democratic government was set up in Russia, effectively knocking Russia out of the war and potentially releasing German troops from the eastern front to the western. Wilson attacked the German submarine policy as “warfare against humanity,” and on April 6 the United States declared war on Germany. Even so, Americans were careful to maintain their separate status, not joining the Allies formally.
German resumption of submarine warfare was the immediate cause of American entry into the war, but there were, of course, other causes. Though neutrality had paid well, interest groups in the United States assumed that war would bring even higher profits.
So much had been lent to the Allied nations that American creditors could not afford to see them defeated. Public opinion was outraged by the German submarine policy. Many Americans feared that their nation’s security would be hurt if Germany were victorious; at the least, the world order would be reorganized.
Perhaps above all, more Americans simply felt emotionally closer to Britain than to the Germans, and they were unprepared to see Europe unified under German domination. Wilson no doubt did not believe that he was embarking on a war to “make the world safe for democracy,” but he did believe that democracy would not be safe if the Central Powers were victorious.