Next, the chapter goes on to talk about the Peace Movement, which was an effort by president Wilson to keep the United Sates out of a "European war" by proclaiming a state of neutrality. His peace effort failed however, as it became impossible to ignore that the United Sates must intervene.
The Zimmermann telegram was an important aspect of the United States aggressive attitude towards Germany. Not only did the telegram outrage congress, but also the general public. The other reason for American intervention was the change in government in Russia. A new liberal-democratic government had been established, and the United Sates felt that it was in their interest to support that government. Now, a defeated Germany would be a beneficial step towards democracy in Europe, as there was no longer a Russian autocratic aggressor on the sidelines.
For these reasons, president Wilson declared war on Germany on April 6th 1917, bringing America into one of the worst conflicts in history.