" Hawks were as appalled as antiwar critics like McGovern , and not just by Lyndon Johnson's bizarre and offensive metaphors . The idea that gradually escalating the bombing of the North would eventually convince Ho Chi Minh to back down struck many as senseless , if not insane . And along with the intensified air strikes came periodic bombing ' pauses ' . LBJ hoped that these temporary cessations of violence might extract concessions that the bombing itself had failed to produce . Predictably , they did not . Hanoi was not about to abandon its objectives . Besides , the bombing pauses only applied to the North . The United States continued to bomb South Vietnam relentlessly and increase its troop levels there . Hanoi also understood that LBJ used the bombing pauses as pretexts to intensify the bombing in the North . He would say , in effect , Hanoi is not backing down in spite of our peaceful overtures , so we must increase the pressure . "
" By the time Lyndon Johnson finally ended the bombing of North Vietnam in 1968 , the claim that Operation Rolling Thunder had been ' restrained ' was less and less credible . Every significant military target except the ports had been hit , many of them repeatedly . And when Nixon renewed the bombing of North Vietnam in 1972 , it was even more systematic , with the ports mined and B52's used in round - the - clock attacks . All told , according to the historian Mark Clodfelter , the bombing killed about 55,000 North Vietnamese civilians. "