In the past I wrote some articles about head coverings worn by religious dignitaries during their service in the army:
A new book about Jewish army rabanim was published in 2013:
Hank, Sabine; Simon, Hermann; Hank, Uwe:
Feldrabbiner in den deutschen Streitkräften des Ersten Weltkrieges
Hentrich & Hentrich Publisher, Berlin 2013, 623 pages
ISBN 978-3-938485-76-7
The book is a very large end exhaustive elaboration about Jewish rabanim during World war I.
"Feldrabbiner" translated is rabanim working on the battlefields.
"Armeerabbiner" translated is rabanim working for the army.
I can highly recommend to purchase this wonderful book for your private library.
On the front of their peaked cap two cocades and a Star of David (between these 2 cocades) were fixed.
Leopold Rosenak is wearing a Südwester hat.
Description of the uniform of the Feldrabbiner
© picture: German Colonial Uniforms