In August, 1964, three North Vietnamese gunboats attacked an American destroyer. This incident was followed by a perceived (but imaginary) second attack. These attacks, although one was not real, led to the US Congress passing the Gulf of Tonkin Resolution, which authorized the president to take “all necessary measures to repel armed attack against the forces of the United States and to prevent further aggression.” Johnson then authorized Operation Rolling Thunder, a massive and ongoing bombing of North Vietnam. He also decided to send the first American ground troops to South Vietnam.