Casey served in the Mechanized Infantry during the command portion of his career. He was the commander of the 3rd Brigade of the 1st Cavalry Division, and the Assistant Division Commander – Maneuver (later Assistant Division Commander – Support) of the 1st Armored Division in Germany. He deployed as part of Operation Joint Endeavor to Bosnia-Herzegovina from July 1996 to August 1997. He and the Rear Command Post staff were based in Slavonski Brod, Croatia. Casey took command of the 1st Armored Division in July 1999.