The escalating diplomatic tension between Washington and Berlin after Germany's resumption of unrestricted U-boat warfare in February 1917 is discussed in this latest post from US blogger Dennis Cross. Here's his summary:
'In February 1917 the World War comes to the doorstep of the United States. Following Germany’s resumption of unrestricted submarine warfare, President Wilson severs diplomatic relations with Germany but stops short of declaring war. Announcing the diplomatic break to a joint session of Congress, he adheres to a policy of “armed neutrality” and declares that the United States will not go to war in the absence of an “overt act.” As the submarine threat causes American shipping to grind to a halt, President Wilson proposes legislation authorizing the arming of merchant ships. The month ends with another major step toward American belligerency as Great Britain, which has intercepted and decoded the Zimmermann Telegram, delivers it to the American Government and President Wilson releases it to the press. German submarines torpedo and sink two British ocean liners, taking the lives of two Americans. In Mesopotamia, the British Army drives the Turks out of Kut-Al-Amara. German forces in France begin a withdrawal to the Hindenburg Line. Mata Hari is arrested in Paris.'
Read the full blog here.