'Đang Trong was the region in Central Vietnam, later enlarged by the Vietnamese southward expansion to become Cochinchina (the name was given by the French during colonization in Indochina). Đang Trong was a kingdom ruled by the Nguyen lords while they claimed to be loyal subjects of the Le emperors in Thang Long (Hanoi). The research results presented in this book show that under the Nguyen Lords not only expanded territory on land, Dai Viet gained more land from Phu Yen to Binh Thuan (1611-1693); but also established sovereignty over islands from Hoang Sa to Truong Sa, along with islands near the mainland such as Cu Lao Cham, Ly Son, Phu Quy, Con Dao and Phu Quoc. The research results also showed that there was a very strict law and trial in Dang Trong, though not mentioned much in other historical documents. The military power was also developed with the powerful navy having made many victories.