About nine o'clock in the evening Colonel Haupt received at Alexandria the information that the enemy's cavalry had attacked our great depot of supplies at Manassas Junction. The telegrapher had barely time to send a message, break the connection of the wires, and hurry away to escape capture. [Footnote: Official Records, vol. xii. pt. iii. p. 680.] It was naturally supposed to be only a cavalry raid, but the interruption of communication with Pope in that crisis was in itself a serious mishap. The first thing to be done was to push forward any troops at hand to protect the railway bridge over Bull Run, and by authority of the War Department Colonel Haupt was authorized to send forward, under Colonel Scammon, the Eleventh and Twelfth Ohio without waiting to communicate with me. They were started very early in the morning of the 27th, going to support a New Jersey brigade under General George W. Taylor which had been ordered to protect the Bull Run bridge. [Footnote: C. W., vol. i. pp. 379, 381.] Ignorant of all this, I was busy on Wednesday morning (27th), trying to learn the whereabouts of the trains with my wagon teams, which had not yet reached Washington, and reported the situation as to my command to the Assistant Secretary of War, Mr. Watson. [Footnote: Official Records, vol. xii. pt. iii. p. 698.] I then learned of Scammon's sudden movement to the front, and of the serious character of the enemy's movement upon Manassas. I marched at once with the two regiments still in Washington, expecting to follow the rest of the command by rail as soon as we should reach Alexandria. Arriving there, I hastened to the telegraph office at the railway station, where I found not only Colonel Haupt, but General McClellan, who had come from Fortress Monroe the night before. Of the Army of the Potomac, Heintzelman's and Porter's corps were already with Pope, Franklin's was at Alexandria, and Sumner's was beginning to arrive. As soon as it was known at the War Department that McClellan was present, General Halleck's correspondence was of course with him, and we passed under his orders. [Footnote: Official Records, vol. xii. pt. iii. pp. 688, 689, 691.] It had already been learned that 'Stonewall' Jackson was with infantry as well as cavalry at Manassas, and that the Bull Run bridge had been burned, our troops being driven back three or four miles from it. McClellan thought it necessary to organize the two corps at Alexandria and such other troops as were there, including mine, first to cover that place and Washington in the possible contingency that Lee's whole army had interposed between General Pope and the capital, and, second, to open communication with Pope as soon as the situation of the latter could be learned. Couch's division was still at Yorktown, and orders had been issued by Halleck to ship 5000 new troops there to relieve Couch and allow his veteran division to join the Potomac Army. [Footnote: _Id_., p. 689.]