The Gulf of Tonkin incident was an international confrontation that led to the United States engaging more directly in the Vietnam War. It consisted of a confrontation on August 2, 1964, when United States forces were carrying out covert amphibious operations close to North Vietnamese territorial waters, which triggered a response from North Vietnamese forces. The United States government falsely claimed that a second incident occurred on August 4, 1964, between North Vietnamese and United States ships in the waters of the Gulf of Tonkin. Originally, US military claims blamed North Vietnam for the confrontation and the ostensible, but in fact imaginary, incident on August 4. Later investigation revealed that the second attack never happened. The official American claim is that it was based mostly on erroneously interpreted communications intercepts. The National Security Agency, an agency of the US Defense Department, had deliberately skewed intelligence to create the impression that an attack had been carried out.

The P 4-class torpedo boat, Soviet designations Project 123-bis and Project 123-K, commonly called the Komsomolets class, were Soviet aluminum-hulled torpedo boats. They were armed with twin heavy machine guns and two 450 mm (17.7 in) torpedoes. A large number of them were exported to allied states such as North Vietnam and China. They saw service in a variety of conflicts including World War II, the First Taiwan Strait Crisis, the Vietnam War and the Turkish Invasion of Cyprus.