Complex sentence: The outstanding issues were challenged again in the mid-twentieth century, beginning in 1948, when combined Kiowa, Apache and Comanche representatives filed suit against the US government for compensation due to the original treaty and subsequent actions, including sales under the unratified Jerome Agreement.
Split into simpler sentences: The outstanding issues were challenged again in the mid-twentieth century, beginning in 1948. Combined Kiowa, Apache and Comanche representatives filed suit against the US government for compensation due to the original treaty and subsequent actions, including sales under the unratified Jerome Agreement.