With the passage of time, as it became more evident that the war would not be decided by a great victory on land, the submarine war assumed increasing centrality in reflection and discussion between German leaders.
In February 1916, in a letter sent to Secretary of State Zimmermann, Chancellor von Bethmann-Hollweg expressed concern about the contradiction between the inevitability of lengthening and radicalizing the submarine war and the increased risks of involvement of the United States of America in the war.
“In contrast with the positions of the high-ranking military and even aside from public opinion, it is impossible to keep the submarine fleet on a leash or limit its action only to the Mediterranean. The extension of its activity to the English coasts obviously accentuates the risk of a conflict with the United States. However, as things are now, we must be aware of this danger. Our task is to seek to reduce the possibility of conflict as scrupulously as possible and to keep open the road to overcome any conflicts by offering excuses or compensation, without arriving at a true outbreak (…).
- Spare without exception all American passenger ships (…)
- Unconditionally spare British passenger ships, perhaps with the exclusion of those that are armed (…)
- Spare all other American ships that are identified as such.
Without reducing significantly the efficiency of the submarine war, the German navy must place themselves in conditions of reducing as much as possible the possibility of conflict.
(…) In practice, things must be organized in this way: the submarines will begin the commercial war in March without official announcements, but taking account of the limited provisions. If we are able to cause significant damages to England, and if things in the fields of land war go well, now we can be even more cautious in stopping neutral ships in the vicinity of the English coasts. After all, we can even run the risk of a rupture with the America; in any case, the more this risk is reduced the more our situation will improve on the various war fronts. Otherwise, we will be forced to stop and trust in good fortune, to be able to avoid up to that time a conflict with America.
On 13 January 1917, Carl Duisberg, a well-known spokesperson for large-scale German industry, expressed his support for unlimited submarine war.
“But now we must decide if we can implement the most effective weapon we have available, the sharpest arrow in our quiver. Friends, for this purpose we can no longer be uncertain or timid; the submarines must finally be put into action. I have the greatest faith in the supreme command and in our supreme commander, who will finally launch unlimited submarine war.
We can defeat our main enemy, our strongest opponents, England, only if we hit them in their nerve center and heart. We do not intend to discuss this today. This matter is in the safest hands. It is, in fact, entrusted to a man who enjoys the full faith of all the German people: Hindenburg."
Extract from the speech delivered by the German ambassador to Washington, Johann von Bernstorff, to the American government to justify the launch of unlimited submarine war, on 31 January 1917.
“For two and a half years, England has used their naval power in a criminal attempt to force Germans to submit by starving them. In brutal disregard for international laws, the group of powers guided by England not only impedes the legitimate commerce of their adversaries, but, using unscrupulous pressure, restricts even neutral countries or forces them to abandon any commercial exchange that displeases the Allied powers, or to limit it according to their arbitrary decrees.
The American government is aware of the steps that were taken to limit England and its allies from going back to respecting the rules of international law and the freedom of the seas. Nevertheless, the British government insists on continuing this war of starvation, which in fact does not touch the military power of its adversaries, but forces women and children, the ill and elderly, to endure, for patriotic spirit, suffering and privations that endanger the vitality of the nation.
The British tyranny thus enlarges, without pity, the suffering of the world, indifferent to the laws of humanity, indifferent to the protests of the neutral powers.
(…) the imperial government may no longer justify before their conscience, the German people, and history itself the failure to use any means that can allow putting an end to the war. Like the President of the United States, even the imperial government had expected to be able to reach this goal through negotiations.
Since the attempts to reach an agreement with the Allied powers were rejected, announcing intensification of the war, the imperial government – to save the well-being of the human race in a general sense and to avoid harming its own people, is now forced to continue to fight for existence, thus using more completely all weapons available.
A trench newspaper, “Im Schützengraben,” on 3 February 1918, the anniversary of the launch of unlimited submarine war, underlined the short-term and long-term results reached.
“Imagine the significance of our submarines sinking the equivalent of 1800 fully loaded railway cars every day, full of items that otherwise would act to our enemies’ advantage in the conduct of the war and their economic life (…). The picture today is clear: we build increasingly larger and always more efficient submarines and in quantities clearly greater than those that sink. Despite their efforts, our adversaries build fewer ships than we sink.
(…) In the past months, many of our submarines returned from long cruises without having found even a convoy and managing to hit only a number very limited of ships. Today, the commercial maritime routes, once so populated, became silent and empty. At the same time, enormous quantities of food are deposited by our enemies in the storehouses of half the world. Just as one example, in Australia, three million tons of grain was destroyed by mice. There are no ships to transport it; at home in England, the poor are hungry, while the rich live as before."
W. Bihl (ed.), Deutsche Quellen zur Geschichte des Ersten Weltkrieges, Darmstadt, 1991, pp. 181, 255, 379s.