By the end of 1919 demobilistation was complete. Belief that there would never be another war, along with drastic national economies, led to a rapid reduction in the size of the Army. The two Regular Royal Scots battalions remained, reverting to the practice of one remaining at home with the other abroad. In 1920 2RS undertook garrison duties in Ireland seeing action in 'The Troubles', at a cost of eight killed or died, and which ended in 1922 with the creation of the Irish Free State, now the Republic of Ireland. In 1926 2RS moved to Egypt just as 1RS were returning to the UK from seven years in Burma, India and Aden. From Egypt 2RS went on to serve in China, India and finally, in 1938, to Hong Kong. That same year 1RS moved from Aldershot to Palestine for a one-year operational tour helping to quell the Arab Revolt - a tour which cost them 16 killed and 42 wounded.

The end of WW2 found 1RS in Burma and 2RS on operations in Palestine. In February 1948 the two Battalions merged into one in Edinburgh. The 56-year period from then until the further merger into the Royal Regiment of Scotland (SCOTS) in 2006 saw many and frequent changes of station and role - often at short notice. These included operational tours in Korea, the Canal Zone, Cyprus (in 1955 and 1974), Suez, the Radfan and Aden, Northern Ireland (13 tours totalling 7½ years), the Falkland Islands, the Gulf, Bosnia and 2 tours in Iraq. Fortunately, in spite of so much time spent on operations or in operational theatres, losses were comparatively light with a total of 23 Royals killed, or died in accidents, including three former members of the Regiment subsequently killed serving with SCOTS Battalions in Afghanistan.