Allegedly two naval destroyers of USA were destroyed in the waters of the Gulf of Tonkin. This was the event after which USA began its full scale involvement in the Vietnam war.
Step-by-step explanation:
USA had been scaling and patrolling around the water of the Gulf of Tornkin for quite a lot of time as it bordered the waters of Vietnam which was beginning to become a war zone with the temperature rising and tensions up with the Soviet Union.
The ships were torpedoes allegedly by the soviets or the Vietnamese. This gave USA the final call to officially enter the war which they had not done until then and were staying away from for diplomatic reasons.