A new question arose in connection with American trade with the neutral countries surrounding Germany.  Great Britain early began to intercept ships carrying oil, gasoline, and copper—­all war materials of prime importance—­on the ground that they either were destined ultimately to Germany or would release goods for sale to Germans.  On November 2, 1914, the English government announced that the Germans wore sowing mines in open waters and that therefore the whole of the North Sea was a military zone.  Ships bound for Denmark, Norway, and Sweden were ordered to come by the English Channel for inspection and sailing directions.  In effect, Americans were now licensed by Great Britain to trade in certain commodities and in certain amounts with neutral countries.

Against these extraordinary measures, the State Department at Washington lodged pointed objections, saying:  “This government is reluctantly forced to the conclusion that the present policy of His Majesty’s government toward neutral ships and cargoes exceeds the manifest necessity of a belligerent and constitutes restrictions upon the rights of American citizens on the high seas, which are not justified by the rules of international law or required under the principle of self-preservation.”

=Germany Begins the Submarine Campaign.=—­Germany now announced that, on and after February 18, 1915, the whole of the English Channel and the waters around Great Britain would be deemed a war zone and that every enemy ship found therein would be destroyed.  The German decree added that, as the British admiralty had ordered the use of neutral flags by English ships in time of distress, neutral vessels would be in danger of destruction if found in the forbidden area.  It was clear that Germany intended to employ submarines to destroy shipping.  A new factor was thus introduced into naval warfare, one not provided for in the accepted laws of war.  A warship overhauling a merchant vessel could easily take its crew and passengers on board for safe keeping as prescribed by international law; but a submarine ordinarily could do nothing of the sort.  Of necessity the lives and the ships of neutrals, as well as of belligerents, were put in mortal peril.  This amazing conduct Germany justified on the ground that it was mere retaliation against Great Britain for her violations of international law.

The response of the United States to the ominous German order was swift and direct.  On February 10, 1915, it warned Germany that if her commanders destroyed American lives and ships in obedience to that decree, the action would “be very hard indeed to reconcile with the friendly relations happily subsisting between the two governments.”  The American note added that the German imperial government would be held to “strict accountability” and all necessary steps would be taken to safeguard American lives and American rights.  This was firm and clear language, but the only response which it evoked from Germany was a suggestion that, if Great Britain would allow food supplies to pass through the blockade, the submarine campaign would be dropped.