Delta Three was the code name for a human underground city on Torgu-Va. In 2367 the city was destroyed by a Tarn 30-kiloton atomic weapon. More than eight-thousand humans were dead or dying including the wife of Karlson. The detonation of the weapon attracted the attention of the USS Enterprise (NCC-1701-D) that was in the Torgu-Va system. (TNG novel: The Forgotten War)