In 1979, Clarke was tapped to join the Army Staff in the Office of the Deputy Chief of Staff for Operations and Plans in the Political-Military Division under future Joint Chiefs of Staff Chairman General John Shalikashvili, who had served on the same MACV advisory team in Vietnam. One of his first assignments was as a member of the Reagan-Carter presidential transition team. Clarke also worked on the ABM Treaty. In early 1982, he left the Pentagon to take command of the 2nd Squadron, 11th Armored Cavalry Regiment in Bad Kissingen, Germany. Clarke and his troopers were responsible for over 150-km of the East-West German border in the Fulda Gap. During this period, the Squadron fielded both the M1 Abrams main battle tank and the M2 Bradley fighting vehicle.