To strike back at England, Germany announced that she would use her submarines to sink ships carrying food to the British Isles.  This happened in February, 1915.  There was a storm of protest from the world in general, but Germany agreed that her submarine commanders should warn each ship of its danger and allow the captain time to get the passengers and crew into boats before the deadly torpedo was shot.  Still the crew, exposed to the danger of the ocean in open boats, and often cast loose miles from shore, were in serious danger.

The laws of nations, as observed by civilized countries in wars up to this time, have said that a blockade, in order to be recognized by all nations, had to be successful in doing the work for which it was intended.  If England really was able to stop every boat sailing for German shores, then all nations would have to admit that Germany was blockaded; but if the Germans were able to sink only one ship out of every hundred that sailed into English ports, Germany could hardly be said to be carrying on a real blockade of England.  In spite of protests from neutral nations who were peaceably trying to trade with all the countries at war, this sinking of merchantmen by submarines went on.

In May, 1915, the great steamship Lusitania was due to sail from New York for England.  A few days before her departure notices signed by the German ambassador were put into New York papers, warning people that Germany would not be responsible for what happened to them if they took passage on this boat.  Very few people paid any attention to these warnings.  With over a thousand persons on board the Lusitania sailed, on schedule time.  Suddenly the civilized world was horrified to hear that a German submarine, without giving the slightest warning, had sent two torpedoes crashing through the hull of the great steamer, sending her to the bottom in short order.  A few had time to get into the boats, but over eight hundred men, women, and children were drowned, of whom over one hundred were American citizens.  Strange as it may seem, this action caused a thrill of joy throughout Germany.  Some of the Germans were horrified, as were people in neutral countries, but on the whole the action of the German navy was approved by the voice of the German people.  With a curiously warped sense of right and wrong the Germans proclaimed that the English and Americans were brutal in allowing women and children to go on this boat when they had been warned that the boat was going to be sunk!  They spoke of this much in the manner in which one would speak of the cruelty of a man who would drive innocent children and women to march in front of armies in order to protect the troops from the fire of their enemies.

A storm of indignation against Germany burst out all over the United States.  Many were for immediate war.  Calmer plans, however, prevailed, and the upshot of the matter was that a stern note was sent to Berlin notifying the Kaiser that the United States could not permit vessels carrying Americans to be torpedoed without warning on the open seas.  The German papers proceeded to make jokes about this matter.  They pictured every French and English boat as refusing to sail until at least two Americans had been persuaded to go as passengers, so that the boat might be under the protection of the United States.