im looking to do a small biography on him, due to the significance of the battle of castle itter (Where Wehrmacht troops fought with the allies to rescue french POW's) but i've so far been unable to find any information regarding his life.
If someone could help put me on the right track i would be greatful
Stephen Harding The last Battle tells about the battle itself, not specifically. But considering his role he will be mentioned.
Also you have the German entry at wikipedia. https://de.wikipedia.org/wiki/Josef_Gangl_(Offizier)
http://www.linkfang.de/wiki/Josef_Gangl_(Offizier)#Literatur
You might get his service record here 003A Gallwitzer, Hans bis Garbe, Rolf http://downloads.sturmpanzer.com/guides/nara_a3343_guide_ssofficerindex.pdf These are stored here. https://www.bundesarchiv.de/index.html.en Copies available here https://www.bundesarchiv.de/imperia/md/content/bundesarchiv_de/benutzung/benutzungsvorbereitung/kopierservice/merkblatt-berl-engl-euro_2007_.pdf
That should give you a start.
SS Major Josef Gangl
As I recall, he was Wehrmacht Heer, not SS.