Complex sentence: He was chief of the Osama bin Laden unit at the Counterterrorist Center from 1996 to 1999 and worked as Special Adviser to the Chief of the bin Laden Unit from September 2001 to November 2004.
Split into simpler sentences: He was chief of the Osama bin Laden unit at the Counterterrorist Center from 1996 to 1999. He worked as Special Adviser to the Chief of the bin Laden Unit from September 2001 to November 2004.