“The government of the United States, therefore, desires to call the attention of the imperial German government with the utmost earnestness to the fact that the objection to their present method of attack against the trade of their enemies lies in the practical impossibility of employing submarines in the destruction of commerce without disregarding those rules of fairness, reason, justice and humanity, which all modern opinion regards as imperative. It is practically impossible for the officers of a submarine to visit a merchantman at sea and examine her papers and cargo. It is practically impossible for them to make a prize of her; and, if they cannot put a prize crew on board of her, they cannot sink her without leaving her crew and all on board of her to the mercy of the sea in her small boats. These facts, it is understood, the imperial German government frankly admit. “We are informed that in the instances of which we have spoken time enough for even that poor measure of safety was not given, and in at least two of the cases cited not so much as a warning was received. Manifestly, submarines cannot be used against merchantmen, as the last few weeks have shown, without an inevitable violation of many sacred principles of justice and humanity. “American citizens act within their indisputable rights in taking their ships and in traveling wherever their legitimate business calls them upon the high seas, and exercise those rights in what should be the well-justified confidence that their lives will not be endangered by acts done in clear violation of universally acknowledged international obligations, and certainly in the confidence that their own government will sustain them in the exercise of their rights. PUBLISHED WARNING DECLARED NO EXCUSE FOR ATTACK