Why did North Ireland, Egypt, Trans-Jordan, Syria, and Palestine fight on the side of the Allies

Though both Jews and Arab Muslims date their claims to the land back a couple thousand years, the current political conflict began in the early 20th century. Jews fleeing persecution in Europe wanted to establish a national homeland in what was then an Arab - and Muslim-majority territory in the Ottoman and later British Empire. The Arabs resisted, seeing the land as rightfully theirs. An early United Nations plan to give each group part of the land failed, and Israel and