Here’s a short story that appeared in Adventure Magazine in the 01 December 1931 issue. The author is listed as Claude Farrère which is a pseudonym of French author Frédéric Charles Pierre Édouard Bargone (1876-1957). Looking at his bio on Wiki it appears he would know much about the French colonies and the ever-simmering conflicts within having been a naval officer lived in Indochina and various other postings abroad.
The story relates the background of two Germans who desert their own army to serve in the Foreign Legion in the late 1800’s. It’s told by the first French officer who inducts them into the Legion and who, years later, bumps into the the talkative one who is now a civilian innkeeper in Indochina.