Complex sentence: Since that time, he has been held at a naval brig in Charleston, South Carolina, and is the only known enemy combatant held in military custody on U.S. soil (others are being held at the Guantanamo Bay detention camp in Cuba).
Split into simpler sentences: Since that time, he has been held at the Naval brig in Charleston, South Carolina. He is the only known enemy combatant to be held in military custody on U.S. soil (others are being held at the Guantanamo Bay detention camp in Cuba).