She studied physical education at the Tuskegee Institute and, after graduating, taught at a high school in Greenwood, Mississippi for a year before enlisting.

[1] Allen then learnt French, interrogation and other intelligence skills and did three tours of duty in the Vietnam War, starting in 1967.

She gathered intelligence and wrote a report which correctly predicted the Tet Offensive ahead of its start in 1968 but this warning was ignored.

On her third tour, she led a team of forty Vietnamese translators in Saigon that analysed enemy documents.

Back in the US, she became the first full-time female instructor of prisoner interrogation at the Army Intelligence Center and then became a counterintelligence specialist.