Three sergeants (Zugsführer) in the Austro-Hungarian Army in Vienna before the war. The one on the left wears what looks like a Franz Joseph Bronze Jubilee Medal. This medal was given to all members of the armed forces in 1898 in celebration of the of the 50year of the Emperor's reign.
"I've taken advantage of the rest to send you a small souvenir from the front. Good health and a quick recovery, and good luck. Tonight the canons fire loudly. Nothing new. The regiment is still at rest, we're told it's for 2 months. Waiting to see you and get a strong handshake."