While Great Britain may be charged with having unwarrantably extended the application of certain rules of international law and may have rendered herself liable to pecuniary damages, she displayed in all her measures a scrupulous regard for human life. Her declaration that "The whole of the North Sea must be considered a military area," was explained as an act of retaliation against Germany for having scattered floating mines on the high seas in the path of British commerce. She did not undertake to exclude neutral vessels from the North Sea, but merely notified them that certain areas had been mined and warned them not to enter without receiving sailing directions from the British squadron. The German decree of February 4, 1915, establishing a submarine blockade or "war zone" around the British Isles, on the other hand, was absolutely without legal justification. It did not fulfill the requirements of a valid blockade, because it cut off only a very small percentage of British commerce, and the first requirement of a blockade is that it must be effective. The decree was aimed directly at enemy merchant vessels and indirectly at the ships of neutrals. It utterly ignored the well-recognized right of neutral passengers to travel on merchant vessels of belligerents. The second decree announcing unrestricted submarine warfare after February 1, 1917, was directed against neutral as well as enemy ships. It undertook to exclude all neutral ships from a wide zone extending far out on the high seas, irrespective of their mission or the character of their cargo. It was an utter defiance of all law. The citizens of neutral countries have always had the right to travel on the merchant vessels of belligerents, subject, of course, to the risk of capture and detention. The act of the German ambassador in inserting an advertisement in a New York paper warning Americans not to take passage on the _Lusitania_, when the President had publicly asserted that they had a perfect right to travel on belligerent ships, was an insolent and unparalleled violation of diplomatic usage and would have justified his instant dismissal. Some action would probably have been taken by the State Department had not the incident been overshadowed by the carrying out of the threat and the actual destruction of the _Lusitania_.