Complex sentence: The militia forces, eager for action provoked both friendly and hostile Indians alike, which lead to many Cayuse resisting, however, they were unable to put up an effective opposition to the firepower of their opponents and were driven into hiding in the Blue Mountains.
Split into simpler sentences: The militia forces, eager for action, provoked both friendly and hostile Indians. Many Cayuse resisted, but they were unable to put up an effective opposition to the firepower of their opponents, and were driven into hiding in the Blue Mountains.