The invasion of Cambodia sparked nationwide U.S. protests as Nixon had promised to deescalate the American involvement. Four students were killed by National Guardsmen in May 1970 during a protest at Kent State University in Ohio, which provoked further public outrage in the United States. The reaction to the incident by the Nixon administration was seen as callous and indifferent, reinvigorating the declining anti-war movement. The U.S. Air Force continued to heavily bomb Cambodia in support of the Cambodian government as part of Operation Freedom Deal.