Above: the Kaiser visits the battleship Oldenburg before the war.

Ever since the initial ‘grey wave’ of the Imperial German Army crested against the trenches of the Western Front, Britain’s blockade has progressively tightened around Germany’s import-dependent industries and agricultural sector like a python. Beginning with a November Admiralty declaration making the North Sea a military zone, the Foreign Office tightened its rules and extended the list of contraband items to include livestock feed, food products, and a broad variety of ‘dual-use’ civilian material that can be repurposed to military ends.

It is just one example of how the war is not going well for the Central Powers these days. The effects of the blockade are already being felt in higher food and commodity prices, shortages, and hunger in Germany’s industrial urban centers. Today, Kaiser Wilhelm II announces a blockade of his own:

All the waters surrounding Great Britain and Ireland, including the whole of the English Channel, are hereby declared to be a war zone.  From February 18 onwards every enemy merchant vessel found within this war zone will be destroyed without it always being possible to avoid danger to the crews and passengers.

Neutral ships will also be exposed to danger in the war zone, as, in view of the misuse of neutral flags ordered on January 31 by the British Government, and owing to unforeseen incidents to which naval warfare is liable, it is impossible to avoid attacks being made on neutral ships in mistake for those of the enemy.

Navigation to the north of the Shetlands, in the eastern parts of the North Sea and through a zone at least thirty nautical miles wide along the Dutch coast is not exposed to danger.

Enforced almost entirely with submarines, the German blockade zone will be expanded on the 18th and then throughout the war, eventually including the French Atlantic coast and the Mediterranean Sea, enlarging as U-boat designs achieve greater endurance and operational range. The Kaiser’s new policy allowing captains to fire torpedoes on unsuspecting neutral merchant shipping, which brings him into direct confrontation with the United States and other neutral countries, is a response to the demands of both his submariners and his soldiers. Erich von Falkenhayn and Paul von Hindenburg may be bitter rivals for control of Germany’s General Staff, but they both agree that unrestricted U-boat warfare is the only way to counter the British blockade.

First and Second Squadron of the High Seas Fleet burn coal just to keep their shipboard lights on

Meanwhile, the Kaiser’s expensive High Seas Fleet, which is too small for a pitched battle with the British Grand Fleet, remains safely at anchor in the Jade Bight. A primary source of prewar tension between the young German empire and the old British one, Wilhem’s battlewagons will have no impact on either empire’s blockade, as he is too risk-averse to use his precious toys for their intended purpose. A series of disastrous surface actions has only deepened his resolve to keep them safe in port.

The new war zone includes the important southwest approaches from the Atlantic. One of the busiest patches of water on the planet, the sea south of Ireland is where most of Britain’s global trade and maritime traffic emerges from its ocean journeys, and is therefore the scene of altogether too many sinkings during the course of the war, including many of the most infamous ones. Altogether, German U-boats will destroy about half of all British merchant shipping of all kinds before the war is over, as captains target everything from passenger liners to fishing trawlers to tramp steamers without warning.

A map of the German blockade zone as defined on the 18th of February. Click image to embiggen

For President Woodrow Wilson, whose objections to the British blockade and its lists of contraband are already a matter of public and diplomatic record, the German blockade is even worse than the one already in place. Britain may be seizing and impounding cargo, but Germany is drowning mariners; the sudden spike in shipping insurance rates threatens to undo all the patient, careful repair work by Wilson’s administration, which has only just managed to stabilize America’s export-based economy after the economic shocks of the war’s outbreak. Worse, the announcement of ‘unrestricted’ U-boat warfare comes just two days after a German agent exploded a bomb at the Vanceboro railway bridge on the US-Canadian border, further inflaming American public opinion. This toxic combination of clandestine activity in North America and submarine warfare in the Atlantic Ocean will eventually become too much for any president to sustain American neutrality.

British newspapers immediately seize of the announcement as the latest example of uncivilized German behavior. The world has already condemned the Kaiser’s armies for targeting cathedrals and civilians with shellfire, while a series of Zeppelin airship and fixed-wing aircraft raids on allied cities has raised international alarm. By issuing excuses and easily-debunked denials, Germany simultaneously feeds the allied propaganda machine with these actions and loses the public debate over them.

I couldn’t find a good comparison of U-boat types from World War I. Here are several U-boat types developed during World War II for various mission profiles. During the First, Germany produced a comparable profusion of models for different missions