Complex sentence: In mid- 1853, the Ahwahneechee returned to the valley, but they subsequently betrayed the hospitality of their former Mono hosts by stealing horses that the Mono had taken from non-indigenous ranchers.
Split into simpler sentences: In mid- 1853, the Ahwahneechee returned to the valley. They later betrayed the hospitality of their former Mono hosts by stealing some horses that the Mono had taken from non-indigenous ranchers.