Complex sentence: When he detected the U.S. militia camp eight miles (13 km) away, Black Hawk sent out peace envoys in order to negotiate a truce, they were told to wave a white flag at the militia.
Split into simpler sentences: When he detected the U.S. militia camp eight miles (13 km) away, Black Hawk sent out peace envoys in order to negotiate a truce. They were told to wave a white flag at the militia.