These general principles left undetermined two important matters: "What is an effective blockade?" and "What is contraband of war?" The task of answering these questions fell to Great Britain as mistress of the seas. Although the German submarines made it impossible for her battleships to maintain a continuous patrol of the waters in front of blockaded ports, she declared the blockade to be none the less "effective" because her navy was supreme. As to contraband of war Great Britain put such a broad interpretation upon the term as to include nearly every important article of commerce. Early in 1915 she declared even cargoes of grain and flour to be contraband, defending the action on the ground that the German government had recently taken possession of all domestic stocks of corn, wheat, and flour.

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.

Violations of American Rights.—Meanwhile Germany continued to ravage shipping on the high seas. On January 28, a German raider sank the American ship, William P. Frye, in the South Atlantic; on March 28, a British ship, the Falaba, was sunk by a submarine and many on board, including an American citizen, were killed; and on April 28, a German airplane dropped bombs on the American steamer Cushing. On the morning of May 1, 1915, Americans were astounded to see in the newspapers an advertisement, signed by the German Imperial Embassy, warning travelers of the dangers in the war zone and notifying them that any who ventured on British ships into that area did so at their own risk. On that day, the Lusitania, a British steamer, sailed from New York for Liverpool. On May 7, without warning, the ship was struck by two torpedoes and in a few minutes went down by the bow, carrying to death 1153 persons including 114 American men, women, and children. A cry of horror ran through the country. The German papers in America and a few American people argued that American citizens had been duly warned of the danger and had deliberately taken their lives into their own hands; but the terrible deed was almost universally condemned by public opinion.

The Lusitania Notes.—On May 14, the Department of State at Washington made public the first of three famous notes on the Lusitania case. It solemnly informed the German government that "no warning that an unlawful and inhumane act will be committed can possibly be accepted as an excuse or palliation for that act or as an abatement of the responsibility for its commission." It called upon the German government to disavow the act, make reparation as far as possible, and take steps to prevent "the recurrence of anything so obviously subversive of the principles of warfare." The note closed with a clear caution to Germany that the government of the United States would not "omit any word or any act necessary to the performance of its sacred duty of maintaining the rights of the United States and its citizens and of safeguarding their free exercise and enjoyment." The die was cast; but Germany in reply merely temporized.

In a second note, made public on June 11, the position of the United States was again affirmed. William Jennings Bryan, the Secretary of State, had resigned because the drift of President Wilson's policy was not toward mediation but the strict maintenance of American rights, if need be, by force of arms. The German reply was still evasive and German naval commanders continued their course of sinking merchant ships. In a third and final note of July 21, 1915, President Wilson made it clear to Germany that he meant what he said when he wrote that he would maintain the rights of American citizens. Finally after much discussion and shifting about, the German ambassador on September 1, 1915, sent a brief note to the Secretary of State: "Liners will not be sunk by our submarines without warning and without safety of the lives of non-combatants, provided the liners do not try to escape or offer resistance." Editorially, the New York Times declared: "It is a triumph not only of diplomacy but of reason, of humanity, of justice, and of truth." The Secretary of State saw in it "a recognition of the fundamental principles for which we have contended."

The Presidential Election of 1916.—In the midst of this crisis came the presidential campaign. On the Republican side everything seemed to depend upon the action of the Progressives. If the breach created in 1912 could be closed, victory was possible; if not, defeat was certain. A promise of unity lay in the fact that the conventions of the Republicans and Progressives were held simultaneously in Chicago. The friends of Roosevelt hoped that both parties would select him as their candidate; but this hope was not realized. The Republicans chose, and the Progressives accepted, Charles E. Hughes, an associate justice of the federal Supreme Court who, as governor of New York, had won a national reputation by waging war on "machine politicians."

In the face of the clamor for expressions of sympathy with one or the other of the contending powers of Europe, the Republicans chose a middle course, declaring that they would uphold all American rights "at home and abroad, by land and by sea." This sentiment Mr. Hughes echoed in his acceptance speech. By some it was interpreted to mean a firmer policy in dealing with Great Britain; by others, a more vigorous handling of the submarine menace. The Democrats, on their side, renominated President Wilson by acclamation, reviewed with pride the legislative achievements of the party, and commended "the splendid diplomatic victories of our great President who has preserved the vital interests of our government and its citizens and kept us out of war."