Complex sentence: Amy Elizabeth Thorpe was an American spy codenamed "CYNTHIA" active in World War Two who worked primarily for the then secret British Security Coordination, a cover name for all British intelligence efforts in the Americas from 1939-1945.
Split into simpler sentences: Amy Elizabeth Thorpe was an American spy codenamed "CYNTHIA" active in World War Two who worked primarily for the then secret British Security Coordination. The BSC was a cover name for all British intelligence efforts in the Americas from 1939-1945.