The document discusses the Gulf of Tonkin Incidents in 1964 which involved attacks on US ships by North Vietnamese vessels and served as the justification for the Gulf of Tonkin Resolution that gave President Johnson broad war powers to escalate US military involvement in Vietnam. It notes that while the US initially had a support and training role in South Vietnam, the Gulf of Tonkin Incidents led to the first significant deployment of US ground forces in a defensive capacity and marked the beginning of large-scale US military involvement in the costly and frustrating Vietnam War.