At this time, however, the submarine campaign itself underwent a change. Previously most of the ships destroyed were sunk off the coast of England, France or in the Mediterranean. During the year and a half of the submarine campaign the Allies' method of catching and destroying submarines became so effective it was too costly to maintain submarine warfare in belligerent waters. The German Navy had tried all kinds of schemes but none was very successful. After the sinking of the _Ancona_ the Admiralty planned for two submarines to work together, but this was not as successful as it might have been. During May, June and July the submarine warfare was practically given up as the losses of ships during those months will show. There was a steep decline from a quarter of a million tons in April to less than 140,000 tons in May, about 125,000 tons in June and not much more than 100,000 tons in July. During these three months the Navy was being bitterly criticised for its inactivity. But as the events six months later will show the German navy simply used these months to prepare for a much stronger submarine campaign which was to begin in August. By this time it was decided, however, not to risk a submarine campaign off the Allied coasts but to operate in the Atlantic, off the coasts of Spain and Norway. This method of submarine warfare proved very successful and by November, 1916, Germany was sinking over 425,000 tons of ships per month. During this swell in the success of the submarine campaign the U-53 was despatched across the Atlantic to operate off the United States coasts. U-53 was sent here for two purposes: First, it was to demonstrate to the American people that, in event of war, submarines could work terror off the Atlantic coast. Second, it was to show the naval authorities whether their plans for an attack on American shipping would be practical. U-53 failed to terrorise the United States, but it proved to the Admiralty that excursions to American waters were feasible. On February 1, when the Kaiser defied the United States by threatening all neutral shipping in European waters, Germany had four hundred undersea boats completed or in course of construction. This included big U-boats, like the U-53, with a cruising radius of five thousand miles, and the smaller craft, with fifteen-day radius, for use against England, as well as supply ships and mine layers. But not all these were ready for use against the Allies and the United States at that time. About one hundred were waiting for trained crews or were being completed in German shipyards.