THE GERMANS' UNLIMITED SUBMARINE WAR
On January 31, 1917, the Germans declared unlimited submarine war on all shipping of every nationality approaching Allied ports.
On February 2, I received in New York the following memorandum from the German Embassy in Washington. To me, the crucial paragraph was:
From February 1, 1917, sea traffic will be stopped with every available weapon and without further notice in the following blockade zones around Great Britain and France, Italy, and in the Eastern Mediterranean. . . .
The notice went on to define in detail the zones where ships would be sunk without warning. The Germans' declaration closed all our approaches to Rotterdam from British ports. The orders did provide a passage through the German mine fields in the North Sea-on condition that the ships proceed from neutral ports directly to Holland without calling at British ports. The Germans further provided that neutral ships near their destinations "will be spared during a suitable time" (later defined as no later than February 4 and thus, as far as we were concerned, a deadline of forty-eight hours).
We also received on February 2 the following from our Director in Brussels, through our Rotterdam office, confirming, in more detail, the German declaration: