In the summer of 1940, after the Battle of France, British General Wavell visited Trans-Jordan and encouraged the doubling in size of the Mechanized Force. The Force was redesigned The Mechanized Regiment of the Arab Legion (of battalion strength).
In May 1941, the Arab Legion Mechanized Regiment participated against pro-Nazi Rashid Ali who had seized power in Iraq and was attacking British forces located there.
The Regiment was equipped with 8 cwt Ford trucks called "Scout Cars", from the USA, and fitted with Lewis guns and Vickers Machine Guns. Each truck had a driver, co-driver, a Lewis gunner and his assistant, and six or more riflemen. There was no artillery or mortars but four of the original homemade armored cars were still a part of the Regiment.
On 1 July 1941, the Vichy French 2nd Light Desert Company attacked Sukhna. The French were held and finally routed by the Arab Legion. The Arab Legion captured six armored cars, four trucks, twelve machine guns, and 80 prisoners of war.
The Mechanized Regiment had it’s name changed then to the 1st Mechanized Regiment. A 2nd Regiment was raised in September 1941 and the 3rd Regiment was formed in November 1941. All three units formed a brigade. The British provided money and uniforms but vehicles still came from Ford in the USA. The Arab Legion also built 100 armored cars to its own.
Rommel’s advance into Egypt in July 1942, caused the Mechanized Brigade to be deployed to the Sinai for a short time, until the battle of El Alamein.
From January to October 1943 the 1st Mechanized Regiment later served under 30th Indian Brigade in Iraq. Plans to deploy the Mechanized Brigade in the Balkans and Italy but this never came about due to Allied success’ in both areas. The Arab Legion ended the war as a static unit protecting strategic resources and communications in the Middle East.
On May 25, 1946, Amirate became a Kingdom and The Arab Legion as they marched in the national parade. On 8 June 1946, a detachment of the Arab Legion took part in the Victory Day parade in London.
After the war, the unit's strength was reduced to roughly 6,000. The unit was equipped with South African Marmon-Herrington Mk IV armored cars, and Canadian Otter scout cars.
The Arab Legion obtained six armored cars manufactured by Wagner, a German firm based in Jaffa, Palestine.