The French colonial forces enthroned Sihanouk as king of Cambodia in 1941. He later abdicated the throne, but maneuvered tirelessly to preserve Cambodia's neutrality during the war. He was ousted in March, 1970 while on a trip to France. Cambodian defense minister Lon Nol led the coup d'etat, an event that opened the way for U.S. and South Vietnamese incursions into Cambodia.