score:8
Found information in the JSTOR article France's Middle Eastern Ambitions, the Sykes-Picot Negotiations, and the Oil Fields of Mosul, 1915-1918*:
Georges Clemenceau ceded Mosul during a Sunday conversation at the French Embassy in London on December 1st 1918. Possibly for one or more of these three reasons:
I suggest reading the entire article to dig into the backstory.
* Had to get a MyJSTOR account to read it.