Complex sentence: These Apache unnits proved more effective than units of the U.S. Cavalry in finding the mountain hideouts of the Apache bands, and killing or capturing them., and it highly unsettling for Geronimo's band to realize their own tribesmen helped find their hiding places.
Split into simpler sentences: These Apache unnits proved more effective than units of the U.S. Cavalry in finding the mountain hideouts of the Apache bands, and killing or capturing them. Additionally it was highly unsettling for Geronimo's band to realize their own tribesmen helped find their hiding places.