Found by Paul Simadas and posted on the
Facebook page https://www.facebook.com/groups/385353788875799
Wilhelm Thöny was born in 1888 in the Austrian province of Styria and died in New York in 1949. He became a painter, graphic artist, engraver and illustrator. Thöny trained at the State Art School in Graz, and then the Academy of Fine Arts, Munich from 1908 to 1912.
In 1915, Thöny volunteered to join the Graz Rifle Regiment #3. In 1916, now as an army artist, he was commissioned to paint portraits of enemy soldiers for the book "The enemies of Germany and its allies” or “Die Feinde Deutschlands und seiner Verbündeten". He visited prisoner of war camps at Braunau in Bohemia, Kleinmünchen and Mauthausen to paint portrait studies of captured Greek, Italian, Albanian and Romanian soldiers.
In the portrait shown here he has painted a Greek soldier in a martial pose showing a certain empathy for his subject:
Wilhelm Thöny is considered one of the most important Austrian artists of the first half of the 20th century, who, according to the latest findings, can be ranked alongside such famous painters as Oskar Kokoschka, Herbert Boeckl or the artists of the Nötscher Kreis like Anton Kolig, Franz Wiegele.
Sources: post by Paul Simadas and Wikipedia