On February 4, 1915, the Germans sent a declaration to all neutral countries informing them that any neutral shipping in an area that the Germans declared to be a "war zone", would be in danger of being destroyed. The American government took this declaration to be a threat.
the German admiralty declaration
" All the waters surrounding Great Britain and Ireland, including the whole of the English Channel, are hereby declared to be a war zone. From February 18 onwards every enemy merchant vessel found within this war zone will be destroyed without it always being possible to avoid danger to the crews and passengers.
Neutral ships will also be exposed to danger in the war zone, as, in view of the misuse of neutral flags ordered on January 31 by the British Government, and owing to unforeseen incidents to which naval warfare is liable, it is impossible to avoid attacks being made on neutral ships in mistake for those of the enemy.
Navigation to the north of the Shetlands, in the eastern parts of the North Sea and through a zone at least thirty nautical miles wide along the Dutch coast is not exposed to danger."
-Theobald von Bethmann-Hollweg
(Source: Primary Documents - German Admiralty Declaration, 4 February 1915)
Neutral ships will also be exposed to danger in the war zone, as, in view of the misuse of neutral flags ordered on January 31 by the British Government, and owing to unforeseen incidents to which naval warfare is liable, it is impossible to avoid attacks being made on neutral ships in mistake for those of the enemy.
Navigation to the north of the Shetlands, in the eastern parts of the North Sea and through a zone at least thirty nautical miles wide along the Dutch coast is not exposed to danger."
-Theobald von Bethmann-Hollweg
(Source: Primary Documents - German Admiralty Declaration, 4 February 1915)
After the German Admiralty Declaration was sent, President Wilson issued a statement that kept America neutral but at the same time contained a thinly veiled warning that the United States government would not tolerate the sinking of any neutral American shipping. The U.S. was gradually being drawn into the war.
the U.S., "Strict Accountability"
Excerpt from the text of U.S. 'Strict Accountability' Warning to Germany ..."The Government of the United State views those possibilities with such grave concern that it feels it to be its privilege, and, indeed, its duty, in the circumstances, to request the Imperial German Government to consider, before action is taken, the critical situation in respect of the relation between this country and Germany - which might arise were the German naval force, in carrying out the policy foreshadowed in the Admiralty's proclamation, to destroy any merchant vessel of the United States or cause the death of American citizens."
(Source: Primary Documents - U.S. 'Strict Accountability' Warning to Germany, 10 February 1915)
(Source: Primary Documents - U.S. 'Strict Accountability' Warning to Germany, 10 February 1915)