On 1 April 1926, the Transjordan Frontier Force was formed from cadre drawn drawn from the Arab Legion, and it consisted of only 150 men and most of them were stationed along Transjordan's roads. During this time the Arab Legion was reduced to 900 men and was also stripped of its machine guns, artillery, and communications troops.
The Legion was the most successful of the Arab armies during the 1948 Arab-Israeli war. With a total strength of just over 6,000, its military contingent consisted of 4,500 men in 4 single battalion sized regiments, each with their own armored car squadrons, and seven independent companies plus support troops. The regiments were organized into two brigades. 1st Brigade contained 1st and 3rd Regiments while 3rd brigade contained 2nd and 4th Regiments. There were also two artillery batteries with four 25-pounders each. Note that on 9 February, 1948 the Trans-Jordan Frontier Force was disbanded with members being absorbed back into The Arab Legion. Although headed by Glubb, now a Lieutenant General, command in the field was by Brigadier Norman Lash.
The Legion was initially withdrawn from Palestine to Transjordanian territory, under instruction from the United Nations, prior to the end of the British Mandate. With the commencement of hostilities the Legion re-entered Palestine with 1st Brigade heading to Nablus and 2nd Brigade heading to Ramallah. The Arab Legion entered Palestine with other Arab Forces on May 15, 1948 using the Allenby, now King Hussein, bridge as they were advancing to cover the approaches from Jenin, in the north to Alaffoula and from Al-Majame'a bridge on the Jordan River to Bissan Alaffoula.
There was considerable embarrassment from the United Kingdom government that British officers were employed in the Legion during the conflict and regular British officers, including a brigade commander, were instructed to return to Transjordan. This led to the bizarre spectacle of British officers leaving their units to return to Transjordan before sneaking back across the border to rejoin the Arab Legion. Without exception all of the affected officers returned to their units. One British MP called for Glubb Pasha to be imprisoned for serving in a foreign army without the King's permission.
At Latrun, the Legion blockaded the Jerusalem highway. Legion troops were involved in the Kfar Etzion massacre. On May 28, 1948, aided by Marmon-Herrington Armoured Cars, they conquered the Jewish Quarter of Jerusalem's Old City (i.e. inside the walls of the Old City), expelled the Jews who lived there and took part in the destruction of the Synagogues therein. The Legion also secured the West Bank for Transjordan.
Units of the Arab Legion were engaged in several battles with the Jewish forces including the following:
On 9 February, 1948 the 3,000 strong Trans-Jordan Frontier Force was disbanded with members being absorbed back into The Arab Legion. so that by the wars end in 1949, the Arab Legion consisted of over 10,000 men manning a 100 mile front, which then expanded to a 400 mile front following the withdraw of Iraqi forces.
On October 10, 1956 an enemy force, estimated at a motorized infantry brigade, supported by medium-range artillery and 10 combat aircraft, attacked the towns of Hubla, Al-Nabi Illias and Azroun. The assaulting troops fought the Arab legion west of Al-Nabi Illias and were forced to withdraw to Qalqilia hills.
It must be noted that the Legion generally stayed out of the 1956 War.
Note: "Pasha" is a Turkish honorary title in one of its various ranks is equivalent to the British title of "Lord".