Home»History and Legacy»Timeline»1966-1967: Taking the Offensive»Opening of the “Vinh Window”

Opening of the “Vinh Window”

October 1, 1967 - October 31, 1967

The RC-130 aircraft whose crew helped open the Vinh Window was a modified C-130 Hercules furnished w
The RC-130 aircraft whose crew helped open the Vinh Window was a modified C-130 Hercules furnished w
The RC-130 aircraft whose crew helped open the Vinh Window was a modified C-130 Hercules furnished with equipment and technology used for electronic surveillance and reconnaissance.

American cryptologists seemingly achieve a breakthrough for tracking enemy activity on the Ho Chi Minh Trail. Officers aboard an RC-130 Airborne Communications Reconnaissance Program (ACRP) aircraft begin intercepting enemy logistics communications from Vinh, North Vietnam, a crucial staging point near the entrance to the Ho Chi Minh Trail. U.S. intelligence agencies can use these communications to learn how many troops are moving down the trail, what they are transporting, and where they are going.
 
This intelligence coup, later known as the “Vinh Window,” partially allows U.S. leaders to quantify enemy infiltration into South Vietnam. However, the volume of perishable intelligence produced by the Vinh Window often overwhelms the National Security Agency’s small number of translators, greatly limiting its usefulness.1

1Thomas R. Johnson, The NSA Period, 1952–Present: American Cryptology During the Cold War, 1945–1989: Book II: Centralization Wins, 1960–1972, United States Cryptologic History (Washington, D.C.: Center for Cryptologic History, National Security Agency, 1995), 313, 539–41; Nigel West, Historical Dictionary of Signals Intelligence (Lanham, MD,: Rowman and Littlefield Publishing Group, 2012) 229; Matthew M. Aid, The Secret Sentry: The Untold History of the National Security Agency (New York, Bloomsbury Press, 2009), 113–14.