The United Kingdom declares war on Germany, after Germany invades Belgium.
Austria-Hungary declares war on Russia and Serbia declares war on Germany.
U.S. President Woodrow Wilson announces the U.S. will remain neutral.
The Battle of Tannenberg begins.
The First Battle of the Marne begins. Trench warfare begins as soldiers on both sides dig in
Battle of Ypres begins.
The United Kingdom announces that the North Sea is a military area, effectively creating a blockade of goods into Germany.
Germany sends the secret Zimmerman Telegram to Mexico in an effort to entice Mexico to join the war. The British intercept and decipher the coded message.