to prevent the coming and going of the German
submarine beneath the waters. All naval warfare was changed in a
moment; new methods and new weapons had to be employed.

At the outset of the war the English and French fleets had set up a
strict blockade of Germany. There were certain substances which were
called "contraband of war" and which, according to the law of nations,
might be seized by one country if they were the property of her enemy.
On the list of contraband were all kinds of ammunition and guns, as
well as materials for making these. England and France, however, added
to the list which all nations before the war had admitted to be
contraband substances like cotton, which was very necessary in the
manufacture of gun-cotton and other high explosives, gasoline--fuel
for the thousands of automobiles needed to transport army supplies,
and rubber for their tires. Soon other substances were added to the
list.

An attempt was made to starve Germany into making peace. The central
empires, in ordinary years, raise only about three-fourths of the food
that they eat. With the great supply of Russian wheat shut off and
vessels from North America and South America not allowed to pass the
British blockade, Germany's imports had to come by way of Holland,
Switzerland, and the Scandinavian countries. When Holland in 1915
began to buy about four times as much wheat as she had eaten in 1913,
it did not take a detective to discover that she was secretly selling
to Germany the great bulk of what she was buying apparently for
herself. In a like manner Switzerland and the Scandinavian countries
suddenly developed a much greater appetite than before the war! The
British blockade grew stricter. It was agreed to allow these countries
to import just enough food for their own purposes. The British trusted
that they would rather eat the food themselves than sell it to Germany
even at very high prices. The Germans soon began to feel the pinch of
hunger. They had slaughtered many of their cows for beef and as a
result grew short of milk and butter.

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 tor