Tonkin, Gulf of

Tonkin, Gulf of, NW arm of the South China Sea, c.300 mi (480 km) long and 150 mi (240 km) wide, between Vietnam and China. The shallow gulf (less than 200 ft/60 m deep) receives the Red River. Haiphong, Vietnam, and Peihai (Pakhoi), China, are the chief ports. An alleged attack (Aug., 1964) by North Vietnamese gunboats against U.S. naval forces stationed in the gulf led to increased U.S. involvement in the Vietnam War (see Tonkin Gulf Resolution).

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Tonkin, Gulf of 

(in Vietnamese, Bac Bo), a bay of the South China Sea on the shores of China and Vietnam.

The Gulf of Tonkin is separated from the open sea by the Luichow Peninsula and the island of Hainan. The gulf reaches 330 km inland. The width of the gulf at its entrance is 241 km, and its depth is 40–82 m. In the north, between Hainan and the continent, the Gulf of Tonkin is connected with the sea by the Hainan Strait. Tides are diurnal; high tide reaches 5.9 m. The port of Haiphong (Democratic Republic of Vietnam) is on the Gulf of Tonkin.