Complex sentence: The group was again redesignated 66th Combat Support Squadron (CSS) and became the host unit at RAF Wethersfield performing whatever duties were necessary to keep the base in a useable, operational state.
Split into simpler sentences: The group was again redesignated 66th Combat Support Squadron (CSS) and became the host unit at RAF Wethersfield. The 66th CSS performed whatever duties were necessary to keep the base in a useable, operational state.