Treaty of Saigon
The Vietnamese conceded in 1862 and signed the Treaty of Saigon. This ensured the free practice of the Catholic religion; opened the Mekong Delta (and three ports in the north, in Tonkin) to trade; and ceded to France the provinces of Biên Hòa, Gia Định and Định Tường along with the islands of Poulo Condore. In 1864 the three annexed provinces were formally constituted as the French colony of Cochinchina. In 1867, French Admiral Pierre de la Grandière forced the Vietnamese to surrender three additional provinces, Châu Đốc, Hà Tiên and Vĩnh Long. With these three additions all of southern Vietnam and the Mekong Delta fell under French control.