Complex sentence: In 1979, as a propaganda of the deed, the group attempted to assassinate Kurdish tribal leader Mehmet Celal Bucak who they claimed exploited the peasants, and collaborated with Turkey.
Split into simpler sentences: In 1979, as an act of "propaganda of the deed," the group tried to assassinate the Kurdish tribal leader Mehmet Celal Bucak. They claimed that he exploited the peasants, and collaborated with Turkey.