WW1, probably western front. Unfortunately the reverse is totally blank, there are no comments or notes.
The one on the left, lower left corner, seems to wear a M1907/10 Feldrock with Swedish cuffs and the one on opposite side to the the right, first row, seems to wear a M1915/16 Bluse, so most probably the photo is taken somewhere between 1916 and 1918.
WW1, probably western front. by honoretpatria.wordpress, on Flickr