Complex sentence: After serving as COS in a Central European capital from 1998-2000, Mr. Slick returned to Langley to lead CIA's Balkan Operations before becoming an Executive Assistant to Deputy Director of Central Intelligence John McLaughlin.
Split into simpler sentences: After serving as Chief of Station in a Central European capital from 1998-2000, Slick returned to Langley to lead the CIA's Balkan Operations. He then became an Executive Assistant to Deputy Director of Central Intelligence John McLaughlin.