These Austro-Hungarian fieldpost stamps were made by overprinting fieldpost stamps from Bosnia Hercegovina with the portrait of Austrian emperor Franz Jozeph.
The portrait of Austrian emperor Franz Jozeph
K.u.K (Kaiserliche und Königliche) Militärpost = Emperial and Royal military post.
K(aiserliche) und K(önigliche) Feldpost = Emperial and Royal field post.
Bosnien Hercegovina = Bosnia Hercegovina.
Kaiserliche und Königliche (Emperial and Royal): The Austro-Hungarian empire was ruled by Franz Jozeph who was emperor for Austria and king for Hungary.
Example of a cancellation during Austro-Hungarian occupation
(K.u.K. Etappenpostambt - Dąbrowa in Polen)