In September 1966, in a famous speech in Phnom Penh in Cambodia, he expressed France's disapproval of the US involvement in the Vietnam War, calling for a US withdrawal from Vietnam as the only way to ensure peace.
The final assignment for Armstrong in the Gemini program was as the back-up Command Pilot for Gemini 11, announced two days after the landing of Gemini 8. The launch was on September 12, 1966, with Conrad and Gordon on board, who successfully completed the mission objectives, while Armstrong served as a capsule communicator (CAPCOM).