After the war ended the 1st Royal Berkshires served in the Allied occupation of the Rhineland. On 16 February 1919 Dempsey returned to the UK on leave. During the summer he played two first-class cricket matches for Sussex against Oxford University and Northamptonshire. The 1st Battalion was re-formed at Chiseldon Camp in Wiltshire in June 1919. In September it was sent to Iraq, where it helped suppress the Iraqi revolt of 1920. In August 1920, the battalion moved to Iran, where formed part of North Persia Force (Norperforce) in the Russian Civil War. While his battalion was stationed in Iran, Dempsey took up Pelmanism. In late 1921 it moved again, this time to Bareilly, India, and Dempsey took over C Company, but in 1922 returned to England for his first leave in almost three years. He went back to India later in the year before returning to England again in 1923, this time to take up an appointment at the Royal Military College, Sandhurst.