Complex sentence: He graduated top of his platoon in Officer Cadet School in 1998, and subsequently attended the United States Basic Underwater Demolition/SEAL Class 237 graduating in February 2002.
Split into simpler sentences: He graduated top of his platoon in Officer Cadet School (Ref) in 1998. He attended United States Basic Underwater Demolition/SEAL Class 237 and graduated in February 2002.