I am listening to 'The Second World War' by Antony Beevor whilst doing domestic stuff. My German wife comes in and notes that the author uses German words such as "wehrmacht", "luftwaffe" and "panzer" when there are perfectly serviceable English words for those things. I have noticed the same trend/habit in many other world war books. English authors don't use the Japanese nouns, so why do many use the German ones?
Something along the lines of 'the wehrmacht attacked...' Vs 'the Japanese army moved into...'
We're not referring to German names for specific units (i.e. Großdeutschland) but every day words for tank, air force and army.
Where does this trend come from?
It helps readers keep a blank slate to understanding foreign military doctrine and organization.
Leaving military jargon untranslated is pretty common in the military history of many periods and countries. If you read Tully and Parshall's Shattered Sword, a recent history of the Imperial Japanese Navy at Midway, you find words like Kido Butai (mobile/strike force, a group of carriers) Shotai (a group of three aircraft) left untranslated. The reason is that translation of terms tends to let the reader make assumptions based on the connotations in English. If you translate Shotai to it's English equivalent, "Flight", readers may assume it means 4 planes instead of 3, because that's the most common English usage. Shotai leaves less ambiguity and in my personal opinion keeps the prose nice and juicy.
The more a bit of military jargon is unique, the more it tends to remain untranslated. A history of the Iran-Iraq war may use Pasadaran to refer to what U.S. newspapers call the Iranian Revolutionary Guards, because they are not exactly the same as other institutions in history called Guards or Guardians. Red Guards in China, Napoleonic Imperial Guards, and Soviet Guard formations are not really like the Pasadaran so using a bit of Persian helps prevent the reader jumping to conclusions.
Of course, German WWII terms are a special case, since it's a decades long tradition in military history to leave them untranslated. I don't really know exact historiography of this tradition, so I'll leave that to others. The other important point in these terms is that the Nazi Regime specifically chose them, Reichwehr became Wehrmacht, Luftstreitkräfte became Luftwaffe and so on. They have specific military, doctrinal, and historical significance which would be lost in translation.