(1) General Paul von Hindenburg, Out of My Life (1934)

On the other hand, in view of England's economic situation, the Imperial Admiralty promises us that by the ruthless employment of an increased number of U-boats we shall obtain a speedy victory, which will compel our principal enemy, England, to turn to thoughts of peace in a few months. For that reason, the German General Staff is bound to adopt unrestricted U-boat warfare as one of its war measures, because among other things it will relieve the situation on the Somme front by diminishing the imports of munitions and bring the futility of the Entente's efforts at this point plainly before their eyes. Finally, we could not remain idle spectators while England, realising all the difficulties with which she has to contend, makes the fullest possible use of neutral Powers in order to improve her military and economic situation to our disadvantage.

(2) Kaiser Wilhelm II issued orders to U-boat commanders on 1st February, 1917.

We will frighten the British flag off the face of the waters and starve the British people until they, who have refused peace, will kneel and plead for it.

(3) President Woodrow Wilson, speech (April 1917)

The new policy, however, has swept every restriction aside. All vessels, irrespective of cargo and flag, have been sent to the bottom, without help and without mercy. Even hospital and relief ships, though provided with the Germans' safe conduct, were sunk with the same reckless lack of compassion or principle.

Germany's submarine warfare is no longer directed against belligerents, but against the whole world. All nations are involved in Germany's action. The challenge is to all mankind. Wanton, wholesale destruction has been effected against women and children while they have been engaged in pursuits which even in the darkest periods of modern history have been regarded as innocent and legitimate.

There is one choice I cannot make. I will not choose the path of submission, and suffer the most sacred rights of the nation and of the people to be ignored and violated.

With a profound sense of the solemn and even tragic character of the step I am taking, and of the grave responsibilities involved, but in unhesitating obedience to my constitutional duty, I advise Congress to declare that the recent course of the German Government is nothing less than war against the United States, and that the United States accept the status of a belligerent which has been thrust upon it, and will take immediate steps to put the country into a thorough state of defence, and to exert all her power and resource in bringing Germany to terms, and in ending the war.