This was the secret 1916 agreement made during World War I between France and Great Britain (with Russia’s agreement), to divide the Ottoman Empire-controlled Middle East into French and British spheres of control. Britain was accorded control over what is present-day Palestine
/Israel, Jordan, and southern Iraq. France was accorded control over what is present-day Lebanon, Syria, northern Iraq and south-eastern Turkey. The Sykes-Picot Agreement is what led to the British Mandate
of Palestine. See "Why border lines drawn with a ruler in WW1 still rock the Middle East
," Tarek Osman, BBC, Dec 14, 2013.