When the French withdrew from Indochina shortly after their defeat in the Battle of Dien Bien Phu, the Americans became increasingly involved in Laos due to the threat of Communist insurgents in Indochina. They saw Laos as one of dominoes in their Domino Theory. Under the leadership of the General Vang Pao, Hmong forces with US support prevented the Pathet Lao and their Vietnamese backers from toppling the Kingdom of Laos. They also rescued downed American pilots, and helped the US, from their base in the "Secret City" of Long Tieng to coordinate bombing missions over Vietnam and Laos.