Complex sentence: The reservation was established by the between the United States and the Shoshone and Bannock tribes in the wake of the Bear River Massacre (1863), when 400 Shoshone were killed by Army troops.
Split into simpler sentences: The reservation was established by the between the United States and the Shoshone and Bannock tribes. This was achieved in the wake of the Bear River Massacre (1863), where 400 Shoshone were killed by Army troops.