Who were the british fighting in the middle east?

With the onset of WWI, the French and the British sent armies and agents into the Middle East, to foment revolts in the Arabian Peninsula and to seize Iraq, Syria, and Palestine. In 1916, French and British diplomats secretly reached the Sykes-Picot agreement, carving up the Middle East into spheres of influence for their respective countries. That agreement was superseded by another which established a mandate system of French and British control, sanctioned by the new League of Nations.