General Pierce advanced to the attack early on the morning of June 9th. The two columns mistook each other, and not until 10 men were killed was the sad blunder discovered. An assault quickly followed, but the assailants were defeated with the loss of 14 killed and 49 wounded. Among the slain was Lieutenant John T. Greble, a brilliant West Point officer, who ought to have been in command of the brigade, with which he doubtless would have achieved a success. The incompetency of the political leader cost dearly, but the government was yet to learn that full-fledged officers are not to be found among men who have made politics their life profession. SUCCESSFUL UNION CAMPAIGN IN WESTERN VIRGINIA. The only place where there were any Union successes was in western Virginia. Colonel Wallace with a detachment of Indiana Zouaves--a favorite form of military troops at the beginning of the war--made a forced march at night over a mountain road, from Cumberland, in Maryland, to Romney, where the Confederates had a battery on a bluff near the village, guarded by a number of field-pieces. By a spirited dash, the Union troops captured the position and drove the defenders into the woods. Unable to overtake them, Colonel Wallace returned to Cumberland. This incident had important results. General Jo Johnston, one of the best commanders of the war, was at Harper's Ferry, and, fearing for his communications, he evacuated the post, and marched up the Shenandoah Valley to a point near Winchester. GENERAL McCLELLAN. The operations in western Virginia brought into prominence an officer who was destined to play an important part in the war. He was George B. McClellan, born in Philadelphia in 1826, and graduated at West Point in 1846. He rendered fine service in the Mexican War, after which, resigning from the army, he was for several years engineer for the Illinois Central Railroad and afterward a railroad president. He was appointed a major-general at the opening of the Civil War, and, with 15,000 troops, mostly from the Western States, he advanced against the Confederates in western Virginia under the command of General Garnett, also a graduate and formerly an instructor at West Point. Garnett held a position west of the principal line of the Alleghanies, which covered the road leading from Philippi to Beverly. Colonel Pegram was placed in charge of the hill Rich Mountain, a short distance south of Garnett.