Reith was commissioned into the
Parachute Regiment on 19 December 1969. He was promoted to lieutenant on 19 June 1971 and to captain on 19 December 1975. He was further promoted to major on 30 September 1980, lieutenant colonel on 30 June 1985 and to colonel on 30 June 1989. Early appointments included 3rd Battalion the Parachute Regiment as a
company commander, tours of Northern Ireland (for which he was
mentioned in despatches on 11 November 1986 and appointed an
Officer of the Order of the British Empire on 31 October 1989), a tour of
Yugoslavia (for which he was awarded the
Queen's Commendation for Valuable Service on 22 November 1994), command of 1st Battalion the Parachute Regiment, and
chief of staff of the
20th Armoured Brigade in Detmold, West Germany. He was advanced to
Commander of the Order of the British Empire in the
1991 Birthday Honours, and promoted to brigadier on 31 December the same year (with seniority from 30 June). On 1 July 1997 he assumed the appointment of Commander
Allied Command Europe Mobile Force (Land), with the rank of major general; during this tour he commanded AFOR, the
NATO-led multinational deployment to
Albania to help resolve the
Kosovo refugee crisis. He also negotiated the undertaking by the KLA to disarm during the closing stages of the crisis. Appointed a
Companion of the Order of the Bath in
2000 New Year Honours, Reith assumed the post of Assistant Chief of Defence Staff (Policy) in the
Ministry of Defence central staff in January. In August 2001 he was appointed
Chief of Joint Operations at the
Permanent Joint Headquarters,
Northwood, and was promoted to lieutenant general on 6 August. During this three-year appointment, he was the joint commander for all worldwide UK overseas operations including
Iraq,
Afghanistan,
the Balkans and
Sierra Leone. He was knighted as a
Knight Commander of the Order of the Bath on 31 October 2003 for services during the invasion of Iraq. Reith
gave evidence to the
Iraq Inquiry on 15 January 2010 regarding this role. Promoted to the acting rank of general in 2003, Reith assumed the appointment of
Deputy Supreme Allied Commander Europe and was promoted to the substantive rank of general from 1 October 2004. He retired from this post in October 2007, and retired from the army on 4 March 2008. ==Retirement==