Complex sentence: The 91st Strategic Reconnaissance Squadron was moved from McGuire AFB, NJ to Johnson AB and Yokota AB, Japan to begin supporting United Nations (UN) troops in Korea, being assigned directly to SAC's Fifteenth Air Force; attached to the FEAF Fifth Air Force.
Split into simpler sentences: The 91st Strategic Reconnaissance Squadron moved from McGuire AFB, NJ to Johnson AB and Yokota AB, Japan to begin supporting United Nations (UN) troops in Korea. It was assigned directly to SAC's Fifteenth Air Force, attached to the FEAF Fifth Air Force.