On 6th April, 1917 , the United States entered the First World War by the following reasons: (i) The Americans were generally more inclined towards England (and her allies) because of their cultural and racial affinity with the English people. Hence, they joined the war in favour of England. (ii) The U.S.A. was the main supplier of arms and other supplies to the Allies, as such she was bound to be implicated in the war. (iii) Economic consideration also prompted the United States to enter the First World War in favour of the Allies. The Allies were in possession of most of the colonies which could give boost to the foreign trade of U.S.A. (iv) The sinking of the U.S.A. ships, carrying the American citizens by the German U-Boats ultimately forced the U.S.A. to join the war.