The Krupp interests have played a leading role in the war, not only by manufacturing billions of shells and cannon, and by financing propaganda in the United States, but by building submarines.  At the Krupp wharves at Kiel some of the best undersea craft are launched.  Other shipyards at Bremen, Hamburg and Danzig have been mobilised for this work, too.  Just a few weeks before diplomatic relations were broken a group of American doctors, who were investigating prison camp conditions, went to Danzig.  Here they learned that the twelve wharves there were building between 45 and 50 submarines annually.  These were the smaller type for use in the English Channel.  At Hamburg the Hamburg-American Line wharves were mobilised for submarine construction also.  At the time diplomatic relations were severed observers in Germany estimated that 250 submarines were being launched annually and that preparations were being made greatly to increase this number.

Submarine warfare is a very exact and difficult science.  Besides the skilled captain, competent first officers, wireless operators and artillerymen, engineers are needed.  Each man, too, must be a “seadog.”  Some of the smaller submarines toss like tubs when they reach the ocean and only toughened seamen can stand the “wear and tear.”  Hence the weeks and months which are necessary to put the men in order before they leave home for their first excursion in sea murder.

But Germany has learned a great deal during two years of hit-and-miss submarine campaigns.  When von Tirpitz began, in 1915, he ordered his men to work off the coasts of England.  Then so many submarines were lost it became a dangerous and expensive military operation.  The Allies began to use great steel nets, both as traps and as protection to warships.  The German navy learned this within a very short time, and the military engineers were ordered to perfect a torpedo which would go through a steel net.  The first invention was a torpedo with knives on the nose.  When the nose hit the net there was a minor explosion.  The knives were sent through the net, permitting the torpedo to continue on its way.  Then the Allies doubled the nets, and two sets of knives were attached to the German torpedoes.  But gradually the Allies employed nets as traps.  These were anchored or dragged by fishing boats.  Some submarines have gotten inside, been juggled around, but have escaped.  More, perhaps, have been lost this way.

Then, when merchant ships began to carry armament, the periscopes were shot away, so the navy invented a so-called “finger-periscope,” a thin rod pipe with a mirror at one end.  This rod could he shoved out from the top of the submarine and used for observation purposes in case the big periscope was destroyed.  From time to time there were other inventions.  As the submarine fleet grew the means of communicating with each other while submerged at sea were perfected.  Copper plates were fastened fore and aft on the outside of submarines, and it was made possible for wireless messages to be sent through the water at a distance of fifty miles.