During the peak of American involvement in Vietnam (1965–73), the DLI stepped up the pace of language training. While regular language training continued unabated, more than 20,000 service personnel studied Vietnamese through the DLI's programs, many taking a special eight-week military adviser "survival" course. From 1966 to 1973, the institute also operated a Vietnamese branch using contract instructors at Biggs Air Force Base near Fort Bliss, Texas (DLI Support Command, later renamed the DLI Southwest Branch). Vietnamese instruction continued at DLI until 2004.