The bad news is the writing says nothing. This might be the photo of the year but the backside was disappointing. At least it wasn't blank!
Wünsdorf, den 7.10.1914
Lieber Schwester,
Teihle ich dir mit daß ich gesund bin und wünsche dir das gleichen.
gruß sendet Gottlob Gronach
Translation:
Wünsdorf (a place about 40 km south of Berlin), 7-10-1914
Dear sister,
I inform you that I'm healthy and wish you the same.
Greetings send, Gottlob Gronach
The adress:
An Fräulein Gronach
Ober Greiffenberg
Angermünde