The expedition of Gen. Burnside into East Tennessee had been conceived in his mind at least six months before it was made. He took command of the department of the Ohio, at Cincinnati, March 25, 1863. It included Indiana, Ohio, Michigan, Illinois, Kentucky (excepting west of the Tennessee River), and “all of East Tennessee that he might at any time occupy.” At that date Gen. Pegram, with a formidable cavalry force, had marched from East Tennessee across the Cumberland River, had driven the United States forces to the north of Kentucky River, and had taken possession of Danville and its vicinity. In a few days, by direction of Gen. Burnside, Gen. Gilmore compelled Gen. Pegram to retreat; and afterwards at Somerset, with the co-operation of Gen. Manson, commanding a part of Gen. Boyle’s forces, completely defeated Pegram, and made the Cumberland River again the dividing line. Central Kentucky was for the next month free from hostile forces. Early in May, upon the organization of the troops in that State into the Twenty-third army corps, under Gen. G. L. Hartsuff, Gen. Burnside at once commenced to make preparations for moving into East Tennessee. On June 3d he left Cincinnati to take command in person of the troops which were organizing for that movement, and which consisted of the two divisions of the Ninth army corps under Gen. Wilcox and a portion of the Twenty-third corps under Gen. Hartsuff. On arriving at Lexington, Ky., he received an order to send the Ninth corps to Gen. Grant, and in consequence, the expedition to East Tennessee had to be deferred. After Col. Sanders returned to Kentucky from his raid, “preparations were still continued” by the General, “in the hope of being able to spare sufficient force to go into East Tennessee.” But they were disturbed by the approach of the rebel General, John H. Morgan, with a large cavalry force, about the 1st of July, on his memorable raid through Kentucky and Indiana into Ohio, which resulted in his surrender near Steubenville, and the capture altogether of 3,000 men--three-fourths of the troops with which he had entered Kentucky. While the United States soldiers were absent in pursuit of Morgan, a considerable force of rebel cavalry under Col. John S. Scott, went from East Tennessee, crossed the Kentucky River and approached the Ohio, evidently with the view of assisting Morgan on his expected return. They were soon driven out of Kentucky with heavy loss, by Col. Sanders’ cavalry after it came back from the pursuit of Morgan.