Unrestricted Submarine Warfare Resumed

With the United States slowly changing into an arsenal of Entente, the submarine warfare is finally restarted.

Unrestricted submarine warfare - which meant that German U-Boats were allowed to torpedo everything that moved around the waters of Entente while not carrying a Central Power bander - was stopped precisely to avoid having United States join the war. While significant part of German General Staff (and especially Ludendorff) disregarded their power, more cautious approach won in the end, especially after fall of Ludendorff.   This merely delayed the inevitable, as the United States' opinion slowly turned towards Entente. With more and more industry of the US working for the sake of Germany's enemies - not to mention growing number of 'volunteers' - German Empire had no other choice that to accept inevitable. And try to at least weaken its influence.   The 'unrestricted submarine warfare' term was however modified, with German Empire's submarines still expected to warn the cargo vessels and have the crew evacuate before firing (at least as long as there were no military ships in the area). This, together with the idea of telling neutral ships to return from the 'restricted zone' on Northern Atlantic - and sinking them only after the ship was detected the second time - was mostly a concession for the civilian government, that hoped to avoid infuriating neutral countries.   While United States ultimately joined the war, the civilian government of German Empire also managed to achieved quite a bit. The idea of United States openly supplying one side of the conflict and using their neutrality as defense against submarines was seen by many as something morally wrong, with even some Americans believing that it was their government that was at least partially responsible for one or two cases of passenger vessels being sunk.   What's more, the sudden spike of casualties in cargo vessels and the fact that many neutral countries suddenly withdrew their maritime trade with Entente forced it to start 'requisitioning' neutral vessels. While an act of panic - for a while it looked like the United Kingdom might actually be blockaded by the submarines, which would happen within a year max - it infuriated many neutral states, especially in Scandinavia and Southern America. While initially it looked like more countries might join the Entente following the outbreak of thaumaturgy, merely United States and Brazil did so in the end.