Complex sentence: In December 1985, Major Thiessen returned to Cherry Point and was assigned to VMA-231 as the Operations Officer, where he led a detachment of six AV-8Bs that deployed to the Mediterranean Sea as part of the 22nd Marine Expeditionary Unit.
Split into simpler sentences: In December 1985, Major Thiessen returned to MCAS Cherry Point and was assigned to VMA-231 as the Operations Officer. While with VMA-231, he led a detachment of six AV-8Bs and deployed to the Mediterranean Sea as part of the 22nd Marine Expeditionary Unit.