The TJFF, while more smartly turned out and drilled than the more pragmatic Arab Legion, was not regarded as an elite force and it must be remembered that it primary role was that of police or gendarmerie.  The Force had encountered great difficulties pacifying the desert tribes and in February 1931, Glubb, second-in-command of the Arab Legion reached an agreement with the TJFF that saw the withdrawal of outlying TJFF detachments from the desert to Zerqa and Ma'an, leaving the desert to be patrolled by Glubb's newly formed Desert Patrol.

In 1933 a second mechanised company was formed and further expansion occurred after the outbreak of the Second World War, in late 1940.  In 1933 also, Lt-Col Shute completed his period of command of the Trans-Jordan Frontier Force, and was succeeded by Major (local Lieutenant-Colonel) CH Miller, 13/18th Hussars.  Throughout this pre-war period, the TJFF was called upon to help quell Arab unrest (in protest at rising Jewish immigration) and, later, to help control Jewish immigration.  At the same time, The Jewish Agency continually called for additional recruitment from the Jewish community.  During November 1937, military forces together with the Police and the Trans-Jordan Frontier Force undertook an extensive operation near the Syrian frontier as a result of which a large gang was located and dispersed with casualties.  The Force frequently participated in this kind of action and there was a steady trickle of casualties.  The cost of operating the Force may be indicated by the British grant for the TJFF for 1938 which was a sum of 200,000 Lebanese pounds.

On 1 January 1941, the cavalry squadrons were formed into 1st Cavalry (Horsed) Regiment at Jisr el Majamie followed in February by the formation of the 1st Mechanised Regiment (from the two mechanised companies) at Irbid.  A Line of Communication Squadron was raised to protect the Baghdad-Haifa road.

The first call to action was something of a disaster.   The Mechanised Regiment was earmarked to join Kingcol, part of Habforce, in the relief of Habbaniya in Iraq in April 1941.  ' D' Company of the Regiment was at the H4 pumping station on the Iraq Petroleum Company pipeline but when ordered to advance against Rutbah, the men refused to cross the border into Iraq.  As a result, the Mechanised Regiment was excluded from the subsequent campaign and ' D' Company was disbanded.  It was replaced by ' L'  Company, formed from the Line of Communication Squadron.  A new squadron, the Mobile Guard Squadron, was formed to take over the line of communication duties.

During this period, the cavalry squadrons were sent to Irbid-Jordan to ensure the security of the region.  A watch was also maintained on the Syrian border in case of infiltration by pro-Axis troops.

A better performance was achieved when in June 1941, both the Cavalry and the Mechanised Regiments joined British and Commonwealth forces in the Syrian campaign.  The TJFF regiments supported the 5th Indian Infantry Brigade advance on Damascus, via Deraa, Sheikh Meskine and Kuneitra.  The TJFF acted as advance guard, scouts and flank protection.  They were given the special task of protecting the railway line, with the horsed and mechanised regiments being given their own sectors to patrol.  Following the conclusion of the campaign, the TJFF left Syria in the Autumn of 1941, leaving behind cadres to instruct the newly formed Syrian and Lebanese armies.

In 1942, the Force was on the Turkish frontier on 'watch and ward' duties.  In November 1943, the Mechanised Regiment left Zerqa for Bandar Abbas on the Persian Gulf to help with the Middle East Anti-Locust campaign.  The regiment spent six months in Persia.  The TJFF was at Jezireh, Syria, in 1944 helping to keep the Syrians and the French apart.  At war's end in 1945, the Mechanised Regiment was in Syria and the Cavalry Regiment in northern Palestine.