At the urgent request of the Secretary of War, the work of restoration was undertaken by Mr. Herman Haupt, a railway engineer who had already distinguished himself more especially as a builder of bridges, and was now to establish a further record as the pioneer of those Construction Corps of which so much was to be heard later on in connection with railways and war. In carrying out the necessary repairs the only help which Haupt could obtain, at first, was that of soldiers detailed from the Federal ranks. Many of these men were entirely unaccustomed to physical labour; others were sickly, inefficient, or unwilling to undertake what they did not regard as a soldier's duties, while the Army officers sent in a fresh lot daily until Haupt's remonstrances led to their allotting certain men to form a "Construction Corps." Other difficulties which presented themselves included an insufficient supply of tools, occasional scarcity of food, and several days of wet weather; yet the work advanced so rapidly that the Akakeek bridge, a single span of 120 ft., at an elevation of 30 ft., was rebuilt in about fifteen working hours; the Potomac Creek bridge, 414 ft. long with an elevation of 82 ft. above the water, and requiring the use of as much roughly-hewn timber as would have extended a total length of six and a half miles, if put end to end, was completed in nine days;[5] and the three miles of track were relaid in three days, included in the work done in that time being the preparation of more than 3,000 sleepers from lumber cut down for the purpose in woods a mile and a half distant from the track. General McDowell subsequently said, concerning the Potomac bridge:-- When it is considered that in the campaigns of Napoleon trestle bridges of more than one story, even of moderate height, were regarded as impracticable, and that, too, for common military roads, it is not difficult to understand why distinguished Europeans should express surprise at so bold a specimen of American military engineering. It is a structure which ignores all rules and precedents of military science as laid down in the books. It is constructed chiefly of round sticks cut from the woods, and not even divested of bark; the legs of the trestles are braced with round poles. It is in four stories--three of trestle and one of crib work. While constructed in so apparently primitive a fashion, the bridge was, General McDowell further said, carrying every day from ten to twenty heavy railway trains in both directions, and had withstood several severe freshets and storms without injury. Thus early, therefore, in the more active phases of the Civil War, evidence was being afforded that, although the railways on which so much depended might be readily destroyed, they could, also, be rapidly restored; and subsequent experience was to offer proofs still more remarkable in support of this fact.