This could well open up another can of worms.

I read the Osprey book about WW2partisan forces, and it mentioned how the Ustasha militia were so brutal the Germans pled with them to be nicer. Or is the book tainted by ethnic propaganda?

If the Nazis asked to be a little 'lighter' I do not know ', could it be, also depends on who, WH or SS? ... however there is also the fact that in part they carried out a "personal" ethnic war towards the Serbs, a distant prelude to the war in the former Yugoslavia of the 90's, Europe is full of these "frictions" of hundreds of years waiting for the right moment to explode again

In what is now part of Croatia and Slovenia between 43-45 there were those that in Italy call "Le Foibe" an ethnic war towards the Italians living in the area of Venezia-Giulia and Dalmatia, this ethnic war it does not have anything to do with the war agaist the Italian fascist regime because all of them were killed, fascists,Civilians, Communist partisan, Socialist partisan and the "Brigate Fiamme Verdi" the Catholic partisans by Tito's partisan militias.

If the book is accurate, the Black Legion seems to wear black-colored Italian uniforms while the rest of them wear conventional Italian unfirms with their own insignia.

The "1st stationary brigade of Ustashi Armed Corces in East Bosnia" was oficial name of mentioned unit and it was stationed in Sarajevo from september 1941. It had 10 infantry companies,4 scout companies, 2 motorised companies, machinegun company, armoured company and 2 batteries of mountain cannons.The nickname Black Legion came from the fact that, due to the lack of all possible military equipment, their uniforms were made from "apropriated" black cloth used to make clothing for priests. Normaly Ustashi uniforms were light green.