WASHINGTON, D. C., Dec. 1--Rear Admiral Alfred Thayer Mahan, U. S. N., retired, America's foremost naval strategist and the world's greatest authority on sea power, died suddenly at the United States Naval Hospital here at 7:15 o'clock this morning of heart disease. Three intimate friends of Admiral Mahan, who met him frequently on his visit to Washington this Winter, expressed the belief tonight that the war in Europe had hastened his death. They said that Admiral Mahan was not only most keenly interested in the great struggle, its relation to sea power, and the naval and strategic problems and lessons being solved or taught by the war, but that the events of the war greatly excited his mind and heart. Admiral Mahan came to Washington on Nov. 1 to take up his labors as a research associate in the Department of Historical Research in the Carnegie Institution, and was pursuing a special line of historical research with a view to writing a history of American expansion and its bearing on sea power. This was to be a monumental work, and he had given thought to it for many years. But he had hardly made a beginning when his heart gave way, overtaxed by his keen interest in the European war. Though he was in his seventy-fourth year, Admiral Mahan was in apparently good health until the war began. The first month of hostilities deeply affected him. There were great demands made upon him for comments as a naval expert, and during the early days of the war he gave many interviews and wrote a number of articles dealing with the contest. The demand on him from American and foreign publications was cut short by President Wilson's order prohibiting American military and naval officers from commenting on the conflict, but Admiral Mahan, while discontinuing his writings on the war, never lost interest in it one moment. Signs of organic heart disease developed in September, and recurred late in October, just before Admiral Mahan came to Washington with Mrs. Mahan and their daughters, Helen and Ellen. Only last week Admiral Mahan visited Secretary Daniels at the Navy Department, and Mr. Daniels said tonight the Admiral was the best-informed man on the war and its lessons he had conversed with. On Saturday the Admiral's condition became such that he decided to enter the naval hospital here. He died in the presence of his wife and two daughters. His son, Lyle Mahan, a New York lawyer, came to Washington tonight. Admiral Mahan was as familiar with Europe, her history, and armaments as he was with American history, and knew many of the men actively identified with the war in high places in England, Germany, and France. Some of his intimate friends among the military and naval men in Europe had lost their lives in the war and this shocked him. Some of these officers he met in his travels, and when he received honorary degrees at Oxford and Cambridge and many more when he went to The Hague in 1899 as American Naval delegate to the First Peace Conference. There were distinct reasons why the American people congratulated themselves upon the presence of Admiral Mahan, then Capt. Mahan, in the First Hague Conference. He was not only a naval strategist and scholar, but was even then regarded as the most eminent living expert in naval strategy. Then he had always consistently advocated strong navies and preparedness for war with special reference to naval influence in making for peace. Added to his equipment as a diplomatist in the delicate and complex task before The Hague Conference was his experience as a public man who had been hailed as the first great exponent of the philosophy of sea power. His great reputation had been developed in the nine years immediately preceding the First Hague Conference. It was in 1890 that his first book of international importance, "The Influence of Sea Power Upon History," was published in Boston and made the author known around the world. This book is really responsible for the German Navy as it exists today. When it was published it was immediately translated into German. Emperor William was so impressed with the book that he ordered a copy placed in the library of every German warship, and ordered all German naval officers to read and study it. Emperor William praised it as the greatest modern work on naval affairs, and the greatest work on sea power. This book taught the Germans the importance of gaining sea power. Admiral Mahan himself had told how it was that he came into the greater work--how, when reading Mommsen in the English Club at Lima, he was struck with that historian's failure to recognize the all-important influence of sea power on Hannibal's history. He wrote out the whole outline of "The Influence of Sea Power," discussed it with Admiral Luce, and then set to work with painstaking method. He chose the term "sea power" with the deliberate purpose of challenging attention. He is the coiner of that term in its present significance. "Purists, I said to myself," he remarked, "may criticize me for marrying a Teutonic word to one of Latin origin, but I deliberately discarded the adjective 'maritime' being too smooth to arrest men's attention. I do not know how far this is usually the case with phrases that obtain currency. My impression is that the originator is himself generally surprised at their taking hold. I was not surprised in that sense. The effect produced was that which I fully proposed, but I was surprised at the extent of my success. 'Sea Power,' in English at least, seems to have come to stay, in the sense I used it. The 'sea powers' were often spoken of before, but in an entirely different manner--not to express, as I meant to, at once an abstract conception and a concrete fact." Admiral Mahan was born at West Point, N. Y., Sept. 27, 1840. His father was D. H. Mahan, an eminent Professor of Engineering at the United States Military Academy. On Nov. 17, 1896, Admiral Mahan was retired on his own application, after forty years' naval service, in order to be able to devote himself to his writings on sea power. Once since then he has been called to active duty--in May, 1898, when he was appointed a member of the Naval War Board, commonly known as the Strategy Board, during the war with Spain. Admiral Mahan was a man of most interesting and admirable personal traits. Slender and erect, he was about 6 feet 2 inches tall, with finely chiseled features, very blue eyes, and a closely-cropped Vandyke beard. He was soft and gentle in voice and had a pleasant but reserved manner, perhaps a little cold to those who did not know him well. He was a man of high religious ideals. Sunday week, while attending service at St. Thomas's Church, he sang all the hymns and chants in the Episcopal service. A naval officer said that the chapters of Admiral Mahan's great work on "The Influence of Sea Power Upon History" were first read as lectures to officers at the Naval War College at Newport and were then published. Two years later appeared his "Influence of Sea Power on the French Revolution and Empire," in the Spring of 1897 his "Life of Nelson, the Embodiment of the Sea Power of Great Britain," and in the following Winter his "Interest of America in Sea Power, Past and Future." Just after his life of Nelson appeared Harold Frederic cabled to The New York Times from London that the reviewers of the London dailies sat up all night with the advance copies to rush long reviews into print the next morning. The Navy Department tonight issued this tribute to Admiral Mahan: "Admiral Mahan became famous as an author and historian in the early nineties, when his books on 'The Influence of Sea Power Upon History' and 'The Influence of Sea Power Upon the French Revolution' were published. These were followed by a 'Life of Nelson.' These books were classics in their line, and were widely read throughout the world. In England and Germany in particular they received the highest commendation, and in every country possessing a navy they became veritable text books in naval strategy. In England the leading naval men of the day confessed that it had remained for him to elucidate the work of the British navy in a way that they themselves had never understood or even dreamed of. "Since his first books he has written many of lesser importance, and these and his essays have kept him before the world as the greatest modern writer on naval strategy. He was a close student of world politics, and his writings on the trend of the politics of the leading nations of the world were accepted as an authority. It may be safely said that no writer of modern times evinced a keener insight in the affairs of the world or expressed himself concerning them more clearly and convincingly than did the late Admiral Mahan. "His death will cause international regret not only because of the high esteem in which he is held in every country of the world interested in naval affairs, but also because of the fact that his death leaves a void among naval and political authorities of the world that no author and writer can fill." At the express request of Admiral Mahan there will be no naval funeral. Simple services will be held at 9 o'clock tomorrow night at St. Thomas's Church. The body will be then taken to the Mahan home at Quogue, L. I., for private interment.