Flag of the Assyrian Volunteers, an ethnic Assyrian military force during WW1, led by Agha Petros.
Own work based on: http://www.assyrianlevies.com/images/Assyrian%20Flag%20during%20World%20War%201%20007_0.jpg and https://i.redd.it/7uuwoqv8vs5z.jpg
Clevelander, Thespoondragon