This is most likely the first photo of a KIA in World War II. This German soldier was killed on the first day of the German invasion of Poland, September 1, 1939, precisely at Hill 179, near Chojnice.
Nazi invasion of Poland
World War II: The Invasion of Poland and the Winter War - In Focus - The Atlantic
World War II begins in 1939 / Germany attacked Poland on September 1, 1939
Polish nurse caught by the Germans during the invasion of Poland, Sept 1939.
World War II Erupts: Color Photos From the Invasion of Poland, 1939. Jewish women and children in Gostynin, Poland, after the German invasion, 1939.
World War II Erupts: Color Photos From the Invasion of Poland, 1939 | LIFE.com
Captured Polish soldiers, 1939.
Near Sochaczew during the German invasion of Poland, 1939.
Adolf Hitler views victory parade in Warsaw after the German invasion of Poland, 1939