DEPTEL 243 , also known as Telegram 243 , the August 24 cable or most commonly Cable 243 , was a high-profile message sent on August 24 , 1963 , by the United States Department of State to Henry Cabot Lodge , Jr. , the US ambassador to South Vietnam . The cable came in the wake of the midnight raids on August 21 by the regime of Ngo Dinh Diem against Buddhist pagodas across the country , in which hundreds were believed to have been killed . The raids were orchestrated by Diem 's brother Ngô Đình Nhu and precipitated a change in US policy . The cable declared that Washington would no longer tolerate Nhu remaining in a position of power and ordered Lodge to pressure Diem to remove his brother . It said that if Diem refused , the Americans would explore the possibility for alternative leadership in South Vietnam . In effect , the cable authorized Lodge to give the green light to Army of the Republic of Vietnam ( ARVN ) officers to launch a coup against Diem if he did not willingly remove Nhu from power . The cable marked a turning point in US-Diem relations and was described in the Pentagon Papers as " controversial " . Historian John W. Newman described it as " the single most controversial cable of the Vietnam War "
raids on August 21
Xá Lợi Pagoda raids
Cable 243