Complex sentence: Adding to the hype, there were many guerrilla groups operating in Kentucky late in 1864 and in 1865, and they often claimed to be part of Sue Munday's gang because of the notorious image.
Split into simpler sentences: Adding to the hype, there were many guerrilla groups operating in Kentucky late in 1864 and in 1865. They often claimed to be part of "Sue Mundy's gang" because of the notorious image.