Great Britain bypassed its mandate from the League of Nations and created Transjordan out of 75% of the land that was supposed to be used for reestablishing the Jewish state--Great Britain just can't seem to stop itself from messing around with the Middle East.
After WW I, it was agreed that "Palestine" was to become a League of Nations Mandate, entrusted to Great Britain.
Under the terms of the Mandate, Britain's principal obligation was to facilitate the implementation of the Balfour Declaration of November 2, 1917, which pledged "the establishment of a national home for the Jewish people." No territorial restrictions whatsoever - neither east nor west of the Jordan River were placed on the Jewish National Home
via psalm122.org