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).
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.