January 19 - Germany sends the secret "Zimmerman Telegram" to Mexico in an effort to entice Mexico to join the war on the German side. The Germans promise Mexico that they will regain Texas and New Mexico if the Central Powers win the war. The British intercept and decipher the coded message and share it with the American government.

February 3 - German Naval Command announces unrestricted submarine warfare in all waters around Britain, France and in the Mediterranean.

February 23 Women in the Russian capital of Petrograd stage a massive demonstration in protest over the shortage of food. The protests are even larger the next day and by February 25, the city of Petrograd was essentially shut down. Police and soldiers join the protesters. On March 15 Tsar Nicholas abdicates and a provisional Pro-Allied Government is established.

March 11th A Second British-Indian expedition in Mesopotamia captures Baghdad. This makes up for the humiliating surrender of the 1916 expedition at Kut. The British expedition continues a slow cautious but successful advance against the Ottoman forces until their final victory in October, 1918

April 6 - The United States declares war on Germany. Many Americans were angered over the U-Boats' unrestricted attacks on shipping, especially when American lives were lost as with the torpedoing of the "Lusitania". Other Americans were infuriated with the "Zimmerman Telegram" and Germany's attempt to get Mexico to fight the USA. American President Wilson argued that the war was really a crusade with democracy fighting against despotism. The sinking of five American merchant ships by U-Boats in March 1917 was the final straw. On April 6th the U.S. Congress voted to declare war on Germany.

While this was good news for the Allies in the long run, it meant little in 1917. It would take almost a year for trained American soldiers to arrive in France in large numbers. By the summer of 1918 500,000 American soldiers were ready for combat in France, with almost 2 million more in training.