Some have wondered what motivated Geronimo to fight so fiercely. Perhaps this from his autobiography (written with S.M. Barrett in 1905) explains a little:
In the summer of 1858, being at peace with the Mexican towns as well as with all the neighboring Indian tribes, we went south into Old Mexico to trade. Our whole tribe (Bedonkohe Apaches) went through Sonora toward Casa Grande, our destination, but just before reaching that place we stopped at another Mexican town called by the Indians Kas-ki-yeh. Here we stayed for several days, camping outside the city. Every day we would go into town to trade, leaving our camp under the protection of a small guard so that our arms, supplies, and women and children would not be disturbed during our absence.
Late one afternoon when returning from town we were met by a few women and children who told us that Mexican troops from some other town had attacked our camp, killed all the warriors of the guard, captured all our ponies, secured our arms, destroyed our supplies, and killed many of our women and children. Quickly we separated, concealing ourselves as best we could until nightfall, when we assembled at our appointed place of rendezvous–a thicket by the river. Silently we stole in one by one: sentinels were placed, and, when all were counted, I found that my aged mother, my young wife, and my three small children were among the slain. There were no lights in camp, so without being noticed I silently turned away and stood by the river. How long I stood there I do not know, but when I saw the warriors arranging for a council I took my place.