Complex sentence: The Behan posse came close to but never engaged the much smaller Earp posse, which not only received help from local businessmen and ranchers, but at one point during the pursuit even wrote a letter to a Tombstone newspaper taunting Behan and his men.
Split into simpler sentences: The Behan posse came close to but never engaged the much smaller Earp posse. The latter received help from local businessmen and ranchers, and at one point, published a letter in a Tombstone newspaper taunting Behan and his men.