At noon on May 29, Lieutenant-Colonel J. G. Vincent and Lieutenant-Colonel E. J. Hall, two of the most brilliant automotive engineers in America, shut themselves in a room of the New Willard Hotel in Washington. When they left that room again on the afternoon of the 31st, though haggard from lack of sleep, they had in their hands the completed assembly drawings of an entirely new airplane engine. Thus was born the famous Liberty engine, about which hundreds of speeches have been made and thousands of columns have been written in scepticism, in criticism, and in praise. As the result of the enthusiastic co-operation of some ten manufacturers, each of whom produced those parts for which his factory was best fitted, the first Liberty, an 8-cylinder, was built in thirty days. The first 12-cylinder engine completed its official endurance test eighty-two days from the time the order for samples was given, the unqualified success of this test removing the Liberty from the realm of experimentation to that of established reputation. In just one year from the day that Lieutenant-Colonels Hall and Vincent pushed the thumb-tacks into their drawing-boards in the hotel room, 1,100 Liberty “twelves” were produced—a remarkable illustration of the ability and ingenuity of American engineers and the energy and resourcefulness of American manufacturers. Thanks to the energetic co-operation of many manufacturers, more than 14,000 Liberty engines had been completed when the Armistice was signed. There are few finer passages in the history of America’s participation in the war than the story of how our manufacturers put aside their private interests and their commercial rivalries and threw themselves and their organizations, heart and soul, into the work of building an airplane that would make America mistress of the skies. When the signing of the Armistice brought our efforts to an abrupt conclusion, there had been developed, tested, and adopted by the army four types of airplanes, production of which would have started early in 1919. They were the Lepere, or L. U. S. A. C. II, a two-seated fighting-plane equipped with a Liberty engine; the U. S. De Havilland 9-A, a day-bombing and reconnaissance plane also fitted with the Liberty engine; the huge Martin bomber, with a gross weight of nearly 5 tons, driven by two Liberty engines; and the Loening, a two-seated combat plane fitted with the 300 horse-power Hispano-Suiza engine.