score:7
This was studied in Germany.
First it was expert testimonial by empirically experienced medics, then it was seen as results in the field and tested on regular soldiers, and finally on a lot of involuntary subjects from concentration camps.
F. Eichholtz: "Die zentralen Stimulantia der Adrenalin‐Ephedrin‐Gruppe", Angewandte Chemie, 1940, DOI
Hans-Diedrich Cremer: "Die Leistungsfähigkeit im Gebirge", Klinische Wochenschrift, August 1943, Volume 22, Issue 34–35, pp 541–546.
H. Staub: "Pharmakologie der Ermüdung", Klinische Wochenschrift, January 1942, Volume 21, Issue 4, pp 73–78
And on D-IX:
Nazi researchers found that equipment-laden holocaust victims (inmates from Sachsenhausen concentration camp) could march in a circle for up to 90 kilometers per day without rest while carrying a 20 kilogram backpack.
But as the allied side also used this in the form of benzedrine it is questionable that the long known effects of cocaine and amphetamine would classify as "German invention".
As the German scientific community took note:
RP Ferrari: "Militärmedizinisches aus dem Auslande", DMW-Deutsche Medizinische Wochenschrift, 1942.
More on this in Nicolas Rasmussen: "Medical Science and the Military: The Allies' Use of Amphetamine during World War II", The Journal of Interdisciplinary History Vol. 42, No. 2 (Autumn 2011), pp. 205-233 (jstor)
Showing that military interest in this started well before the war:
The Flying Personnel Research Committee (fprc), organized shortly before the war by the Air Ministry and chaired by Edward Mellanby - the head of the Medical Research Council - included military men alongside academic scientists as active participants. The British studies (like the American) can be roughly grouped into two categories, field studies by the military and lab studies conducted by civilian experts. From the outset, the British hoped for true performance enhancement from the amphetamines, and not just a new "wakey- wakey" pill to replace the venerable caffeine
That is: both sides explored the potentials of these drugs before the war and not just after seeing German troops perform in blitzkrieg.
From the misleadingly titled "US and Britain gave their troops AMPHETAMINES in the Second World War to 'enhance performance' after learning the Nazis were using a ‘super-drug’ that was the early version of crystal meth"