It took a number of treaties to end the Great War, each covering a different part of the German, Austrian and Ottoman Empires. The last of these was settled by the Treaty of Sevres and later, the Treaty of Lausanne. And to the south of Turkey, it set up two League of Nations Mandates.
The idea of the mandates was a step away from outright colonialism, which involved managing the two regions until a local government could take over.
The British Mandate covered Iraq, Palestine and Transjordan. The French Mandate covered what is now Syria and Lebanon. It faced fierce opposition from the start, notably from Syria, which went to war with the French and lost, though there were intermittent bouts of unrest afterwards.
The French split the territory