In the Saturday Night Massacre, President Richard Nixon essentially forced two Attorneys General to resign so that he could find one who would fire Archibald Cox, the special prosecutor who was appointed to investigate the Watergate affair.
After the Watergate burglary came to light, Nixon’s Attorney General, Elliott Richardson, promised to appoint a special prosecutor to investigate. He appointed Cox and he promised not to fire Cox except for cause. Only the Attorney General was allowed by law to fire Cox and Richardson promised not to do so.
However, Cox eventually subpoenaed the infamous tapes of conversations held by Nixon in the Oval Office. He refused a compromise the Nixon tried to offer to avoid turning the tapes over. Nixon then ordered Richardson to fire Cox. Richardson did not want to go back on his word and therefore resigned rather than fire Cox. Richardson’s deputy, William Ruckelshaus, did the same. Finally, Nixon got Robert Bork, who was Solicitor General and by then acting head of the Justice Department, to fire Cox.
This was called the Saturday Night Massacre because of the resignations of the Attorney General and his deputy and the later firing of Cox.