The United States of America remained neutral in the Great War for three years before entering to become one of the Allied powers. There were many factors leading up to America's entrance into the war. A lot of it was propaganda but some of it had truth to it. Many of the stories of the cruelty of the Central Powers to the Allies were made up to gain more support. Another reason America joined the war with the Allies was that we loaned most of our money and supplies to the Allied powers and we wanted to ensure that we would be paid back. America was kind of justified in entering the war because Germany was destroying passenger ships with American citizens on them and planning war strategies against America such as the plans stated in the Zimmerman note.
The Senate voted for war on April 4th, 1917 and the House of Representatives did the same on April 6th. Many things brought this about such as the Zimmerman note, the sinking of American merchant ships by German U-boats and the overthrow of the czar in Russia. America protested against the sinking of non-combatant ships by the German U-boats especially American vessels. This was stopped for a while but was re-instituted because there was a chance that it might help Germany win the war. The Zimmerman note was a note from the German foreign minister to the German ambassador in Mexico. It never got through to Mexico but was instead intercepted by British agents. It suggested an alliance between Germany and Mexico should the United States decide to enter into the war. Germany said it would support Mexico in recovering territories lost to the United States such as Texas and New Mexico. In March of 1917 the czar of Russia was overthrown and a more democratic government was set up. Now the people who wanted America to enter into the war on the side of the Allies said that it was a war of democracies versus monarchies or dictatorships. President Wilson decided to ask Congress to declare war on the Central Powers and it happened.