On November 9th, General Halleck was appointed commander of the new Department of the Missouri, including that portion of Kentucky west of the Cumberland River. One-half of the force which Fremont had assembled at Springfield was stationed along the railway from Jefferson City to Sedalia, its western terminus, and General Pope was put in command of this force, as well as a district designated Central Missouri. General Price advanced into Missouri as far as Osceola, on the southern bank of the Osage River, from which point he sent parties in various directions, and where he received detachments of recruits. On December 15th, Pope moved out from Sedalia directly to the south, as if he were pushing for Warsaw, and at the same time sent a cavalry force to the southwest, to mask his movement from Price's command at and near Osceola. Next day a forced march took him west to a position south of Warrensburg, and between the two roads leading from Warrensburg to Osceola. The same night he captured the pickets, and thereby learned the precise locality of a body of 3,200 men, moving from Lexington south to join Price. A flying column under Lieutenant-Colonel Brown, sent out the same night, came upon the camp, drove out the command, kept up the pursuit all night, and all the next day and night, pushing the fugitives away from Price and utterly dispersing them over the country, and rejoined Pope on the 18th with 150 prisoners, and sixteen wagons loaded with supplies captured. At the same time Major Hubbard with his detachment pushed south to the lines of one of Price's divisions, encamped opposite Osceola, on the north shore of the Osage, and captured pickets and one entire company of cavalry, with its tents and wagons. On the 18th, Pope moved to the north, to intercept another body moving south to join Price, and which he learned from his scouts would camp that night at the mouth of Clear Creek, just beyond Warrensburg. His dispositions were so made and carried out that the entire body was surrounded and captured, comprising parts of two regiments of infantry and three companies of cavalry--numbering 1,300 officers and men, with complete train and full supplies. Pope's troops reoccupied their camps at Sedalia and Otterville just one week after they marched out of them. Price broke up his camp at Osceola in haste, and fell rapidly back to Springfield.