He is a fictive character who serves our purposes. The following dialogue reveals some key details about the Colonel:

Col. Lin Nan: “You’re white. You shouldn’t be in China at all.”

Gladys Aylward: “How can you say that, when you’re part white?”

LN: “I’m half-white. In your world, I can only be a second-class citizen. I chose China because here, I’m allowed to be of value.”

GA: “That’s why I came here. To be of value.”