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 Ngô Đình Diệm against Buddhist pagodas across the country, in which hundreds were believed to have been killed. The raids were orchestrated by Diệm'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 Diệm to remove his brother. It said that if Diệm 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 Diệm 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." The historian John M. Newman described it as "the single most controversial cable of the Vietnam War."[1]
The cable also highlighted an internal split in the Kennedy administration, with anti-Diệm officials in the State Department prevailing over generals and Department of Defense officials who remained optimistic that the Vietnam War was proceeding well under Diệm. That was underlined by the manner in which the cable was prepared before it was transmitted to Lodge.