Complex sentence: In 1858, he and the Mohave attacked the Rose-Baley Party, which led to his incarceration by the United States Department of War in May 1859.
Split into simpler sentences: In 1858, he and the Mohave attacked the Rose-Baley Party. His role in the attack on the Rose-Baley Party led to his incarceration by the United States Department of War in May 1859.