Complex sentence: Confederate Col. Joseph C. Porter had been recruiting in the Macon area, to the south of Kirksville, with a brigade of 1,500--2,500 ill-trained and poorly-supplied troops, and his irregulars had harried and recruited as far north as Memphis.
Split into simpler sentences: Confederate Col. Joseph C. Porter had been recruiting in the Macon area, to the south of Kirksville. He had assembled a brigade of between 1,500 and 2,500 ill-trained and poorly equipped troops, but his irregulars had harried and recruited as far north as Memphis.